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970 CAPÍTULO 13 Funciones de varias variables
13.10 Multiplicadores de Lagrange
■ Entender el método de los multiplicadores de Lagrange.■ Utilizar los multiplicadores de Lagrange para resolver problemas de optimización con
restricciones.■ Utilizar el método de multiplicadores de Lagrange con dos restricciones.
Multiplicadores de LagrangeMuchos problemas de optimización tienen restricciones, o ligaduras, para los valores quepueden usarse para dar la solución óptima. Tales restricciones tienden a complicar los pro-blemas de optimización porque la solución óptima puede presentarse en un punto fronteradel dominio. En esta sección se estudia una ingeniosa técnica para resolver tales problemas.Es el método de los multiplicadores de Lagrange.
Para ver cómo funciona esta técnica, supóngase que se quiere hallar el rectángulo deárea máxima que puede inscribirse en la elipse dada por
Sea (x, y) el vértice del rectángulo que se encuentra en el primer cuadrante, como se mues-tra en la figura 13.78. Como el rectángulo tiene lados de longitudes 2x y 2y, su área estádada por
Función objetivo.
Se quieren hallar x y y tales que es un máximo. La elección de (x, y) está restringi-da a puntos del primer cuadrante que están en la elipse
Restricción.
Ahora, considérese la ecuación restrictiva o de ligadura como una curva de nivel fija de
Las curvas de nivel de f representan una familia de hipérbolas En estafamilia, las curvas de nivel que satisfacen la restricción dada corresponden a hipérbolas quecortan a la elipse. Es más, para maximizar se quiere hallar la hipérbola que justo sa-tisfaga la restricción. La curva de nivel que hace esto es la que es tangente a la elipse, comose muestra en la figura 13.79.
f !x, y",
f !x, y" ! 4xy ! k.
g!x, y" !x2
32 "y2
42.
x2
32 "y2
42 ! 1.
f !x, y"f !x, y" ! 4xy.
x2
32 "y2
42 ! 1.
Elipse:x2 y2
= 132 42+
x
y
2
2 4
1
1
3
−2
−2−4−1
−1
−3
(x, y)
Función objetivo: Figura 13.78
f !x, y" ! 4xy
x
y
2
2 4 5 6
5
1
1
3
−2
−2−1
−1
−3
Curvas de nivel f:4xy = k
k = 24k = 40k = 56k = 72
Restricción:
Figura 13.79
g!x, y" !x2
32 "y2
42 ! 1
JOSEPH-LOUIS LAGRANGE (1736-1813)
El método de los multiplicadores deLagrange debe su nombre al matemáticofrancés Joseph Louis Lagrange. Lagrangepresentó el método por primera vez en sufamoso trabajo sobre mecánica, escritocuando tenía apenas 19 años.
Larson-13-10.qxd 3/12/09 19:23 Page 970
976 CAPÍTULO 13 Funciones de varias variables
En los ejercicios 1 a 4, identificar la restricción o ligadura y lascurvas de nivel de la función objetivo mostradas en la figura.Utilizar la figura para aproximar el extremo indicado, suponien-do que x y y son positivos. Utilizar los multiplicadores deLagrange para verificar el resultado.
1. Maximizar 2. Maximizar Restricción Restriccióno ligadura: o ligadura:
3. Minimizar 4. Minimizar Restricción o ligadura: Restricción o ligadura:
En los ejercicios 5 a 10, utilizar multiplicadores de Lagrange parahallar el extremo indicado, suponer que x y y son positivos.
5. Minimizar Restricción:
6. Maximizar Restricción:
7. Maximizar Restricción:
8. Minimizar Restricción:
9. Maximizar Restricción:
10. Minimizar Restricción:
En los ejercicios 11 a 14, utilizar los multiplicadores de La-grange para hallar los extremos indicados, suponiendo que x, yy z son positivos.
En los ejercicios 15 y 16, utilizar los multiplicadores de Lagran-ge para hallar todos los extremos de la función sujetos a larestricción
15. 16.
En los ejercicios 17 y 18, utilizar los multiplicadores de La-grange para hallar los extremos de indicados sujetos a dosrestricciones. En cada caso, suponer que x, y y z son no nega-tivos.
17. Maximizar Restricción:
18. Minimizar Restricción:
En los ejercicios 19 a 28, usar los multiplicadores de Lagrangepara encontrar la distancia mínima desde la curva o superficieal punto indicado. [Sugerencia: En el ejercicio 19, minimizar
sujeta a la restricción x + y = 1. En el ejercicio25, usar la operación raíz de una herramienta de graficación.]
En los ejercicios 29 y 30, hallar el punto más alto de la curva deintersección de las superficies.
29. Cono: Plano:30. Esfera: Plano: 2x ! y " z # 2x2 ! y2 ! z2 # 36,
x ! 2z # 4x2 ! y2 " z2 # 0,
f !x, y" ! x2 " y2
x ! y # 12x ! 2z # 6,f #x, y, z$ # x2 ! y2 ! z2
x " y ! z # 0x ! y ! z # 32,f #x, y, z$ # xyz
f
f #x, y$ # e"xy%4f #x, y$ # x2 ! 3xy ! y2
x2 " y2 ≤ 1.
2x ! 4y " 15 # 0f #x, y$ # &x2 ! y2
x ! y " 2 # 0f #x, y$ # &6 " x2 " y2
x2y # 6f #x, y$ # 3x ! y ! 102x ! y # 100
f #x, y$ # 2x ! 2xy ! y2y " x2 # 0
f #x, y$ # x2 " y2
976 Chapter 13 Functions of Several Variables
13.10 Exercises See www.CalcChat.com for worked-out solutions to odd-numbered exercises.
31. Explain what is meant by constrained optimizationproblems.
32. Explain the Method of Lagrange Multipliers for solvingconstrained optimization problems.
WRITING ABOUT CONCEPTS
In Exercises 1– 4, identify the constraint and level curves of theobjective function shown in the figure. Use the figure to approx-imate the indicated extrema, assuming that and are positive.Use Lagrange multipliers to verify your result.
1. Maximize 2. MaximizeConstraint: Constraint:
3. Minimize 4. MinimizeConstraint: Constraint:
In Exercises 5–10, use Lagrange multipliers to find the indicated extrema, assuming that and are positive.
5. MinimizeConstraint:
6. MaximizeConstraint:
7. MaximizeConstraint:
8. MinimizeConstraint:
9. MaximizeConstraint:
10. MinimizeConstraint:
In Exercises 11–14, use Lagrange multipliers to find theindicated extrema, assuming that and are positive.
11. MinimizarRestricción o ligadura:
12. MaximizarRestricción o ligadura:
13. MinimizarRestricción:
14. MinimizarRestricción:
In Exercises 15 and 16, use Lagrange multipliers to find anyextrema of the function subject to the constraint
15.
16.
In Exercises 17 and 18, use Lagrange multipliers to find theindicated extrema of subject to two constraints. In each case,assume that and are nonnegative.
17. MaximizeConstraints:
18. MinimizeConstraints:
In Exercises 19–28, use Lagrange multipliers to find the mini-mum distance from the curve or surface to the indicated point.[Hints: In Exercise 19, minimize subject to theconstraint In Exercise 25, use the root feature of agraphing utility.]
19. Recta:20. Recta:21. Recta:22. Recta:23. Parábola:24. Parábola:25. Parábola:26. Círculo:
27. Plano:28. Cono:
In Exercises 29 and 30, find the highest point on the curve ofintersection of the surfaces.
29. Cone: Plane:30. Sphere: Plane: 2x y z 2x2 y2 z2 36,
x 2z 4x2 y2 z2 0,
4, 0, 0z x2 y2
2, 1, 1x y z 1PuntoSuperficie0, 10x 4 2 y2 4
12, 1y x2 1
3, 0y x2
0, 3y x2
1, 0x 4y 30, 2x y 40, 02x 3y 10, 0x y 1PuntoCurva
x 1 y 1.f x, y x2 1 y2
x y 12x 2z 6,f x, y, z x2 y2 z2
x y z 0x y z 32,f x, y, z xyz
zy,x,f
f x, y e xy 4
f x, y x2 3xy y2
x2 1 y2 1.
x y 10f x, y x2 10x y 2 14y 28x y z 1
f x, y, z x2 y2 z2
x y z 3 0f x, y, z xyz
x y z 9 0f x, y, z x2 y2 z2
zy,x,
2x 4y 15 0f x, y x2 y2
x y 2 0f x, y 6 x2 y2
x2y 6f x, y 3x y 10
2x y 100f x, y 2x 2xy y2y x2 0f x, y x2 y2
x 2y 5 0f x, y x2 y2
yx
2
2−2
−2
c = 1c = 1
2
y
4
4
c = 2c = 4c = 6c = 8
−4
−4
y
2x 4y 5x y 4 0z x2 y2z x2 y2
2
2
4
4
6
6
c = 2c = 4c = 6
y
2
2
4
4
6
6
8
8
10
10
12
12c = 30c = 40c = 50
y
2x y 4x y 10z xyz xy
yx
1053714_1310.qxp 10/27/08 12:10 PM Page 976
976 Chapter 13 Functions of Several Variables
13.10 Exercises See www.CalcChat.com for worked-out solutions to odd-numbered exercises.
31. Explain what is meant by constrained optimizationproblems.
32. Explain the Method of Lagrange Multipliers for solvingconstrained optimization problems.
WRITING ABOUT CONCEPTS
In Exercises 1– 4, identify the constraint and level curves of theobjective function shown in the figure. Use the figure to approx-imate the indicated extrema, assuming that and are positive.Use Lagrange multipliers to verify your result.
1. Maximize 2. MaximizeConstraint: Constraint:
3. Minimize 4. MinimizeConstraint: Constraint:
In Exercises 5–10, use Lagrange multipliers to find the indicated extrema, assuming that and are positive.
5. MinimizeConstraint:
6. MaximizeConstraint:
7. MaximizeConstraint:
8. MinimizeConstraint:
9. MaximizeConstraint:
10. MinimizeConstraint:
In Exercises 11–14, use Lagrange multipliers to find theindicated extrema, assuming that and are positive.
11. MinimizarRestricción o ligadura:
12. MaximizarRestricción o ligadura:
13. MinimizarRestricción:
14. MinimizarRestricción:
In Exercises 15 and 16, use Lagrange multipliers to find anyextrema of the function subject to the constraint
15.
16.
In Exercises 17 and 18, use Lagrange multipliers to find theindicated extrema of subject to two constraints. In each case,assume that and are nonnegative.
17. MaximizeConstraints:
18. MinimizeConstraints:
In Exercises 19–28, use Lagrange multipliers to find the mini-mum distance from the curve or surface to the indicated point.[Hints: In Exercise 19, minimize subject to theconstraint In Exercise 25, use the root feature of agraphing utility.]
19. Recta:20. Recta:21. Recta:22. Recta:23. Parábola:24. Parábola:25. Parábola:26. Círculo:
27. Plano:28. Cono:
In Exercises 29 and 30, find the highest point on the curve ofintersection of the surfaces.
29. Cone: Plane:30. Sphere: Plane: 2x y z 2x2 y2 z2 36,
x 2z 4x2 y2 z2 0,
4, 0, 0z x2 y2
2, 1, 1x y z 1PuntoSuperficie0, 10x 4 2 y2 4
12, 1y x2 1
3, 0y x2
0, 3y x2
1, 0x 4y 30, 2x y 40, 02x 3y 10, 0x y 1PuntoCurva
x 1 y 1.f x, y x2 1 y2
x y 12x 2z 6,f x, y, z x2 y2 z2
x y z 0x y z 32,f x, y, z xyz
zy,x,f
f x, y e xy 4
f x, y x2 3xy y2
x2 1 y2 1.
x y 10f x, y x2 10x y 2 14y 28x y z 1
f x, y, z x2 y2 z2
x y z 3 0f x, y, z xyz
x y z 9 0f x, y, z x2 y2 z2
zy,x,
2x 4y 15 0f x, y x2 y2
x y 2 0f x, y 6 x2 y2
x2y 6f x, y 3x y 10
2x y 100f x, y 2x 2xy y2y x2 0f x, y x2 y2
x 2y 5 0f x, y x2 y2
yx
2
2−2
−2
c = 1c = 1
2
y
4
4
c = 2c = 4c = 6c = 8
−4
−4
y
2x 4y 5x y 4 0z x2 y2z x2 y2
2
2
4
4
6
6
c = 2c = 4c = 6
y
2
2
4
4
6
6
8
8
10
10
12
12c = 30c = 40c = 50
y
2x y 4x y 10z xyz xy
yx
1053714_1310.qxp 10/27/08 12:10 PM Page 976
x
2
2−2
−2
c = 1c = 1
2
y
x
4
4
c = 2c = 4c = 6c = 8
−4
−4
y
2x ! 4y # 5x ! y " 4 # 0
z # x2 ! y2z # x2 ! y2
x
2
2
4
4
6
6
c = 2c = 4
c = 6
y
2
2
4
4
6
6
8
8
10
10
12
12
x
c = 30c = 40
c = 50
y2x ! y # 4x ! y # 10
z # xyz # xy
Desarrollo de conceptos31. Explicar qué se quiere decir con problemas de optimización
con restricciones.32. Explicar el método de los multiplicadores de Lagrange para
resolver problemas de optimización con restricciones.
13.10 Ejercicios976 Chapter 13 Functions of Several Variables
13.10 Exercises See www.CalcChat.com for worked-out solutions to odd-numbered exercises.
31. Explain what is meant by constrained optimizationproblems.
32. Explain the Method of Lagrange Multipliers for solvingconstrained optimization problems.
WRITING ABOUT CONCEPTS
In Exercises 1– 4, identify the constraint and level curves of theobjective function shown in the figure. Use the figure to approx-imate the indicated extrema, assuming that and are positive.Use Lagrange multipliers to verify your result.
1. Maximize 2. MaximizeConstraint: Constraint:
3. Minimize 4. MinimizeConstraint: Constraint:
In Exercises 5–10, use Lagrange multipliers to find the indicated extrema, assuming that and are positive.
5. MinimizeConstraint:
6. MaximizeConstraint:
7. MaximizeConstraint:
8. MinimizeConstraint:
9. MaximizeConstraint:
10. MinimizeConstraint:
In Exercises 11–14, use Lagrange multipliers to find theindicated extrema, assuming that and are positive.
11. MinimizarRestricción o ligadura:
12. MaximizarRestricción o ligadura:
13. MinimizarRestricción:
14. MinimizarRestricción:
In Exercises 15 and 16, use Lagrange multipliers to find anyextrema of the function subject to the constraint
15.
16.
In Exercises 17 and 18, use Lagrange multipliers to find theindicated extrema of subject to two constraints. In each case,assume that and are nonnegative.
17. MaximizeConstraints:
18. MinimizeConstraints:
In Exercises 19–28, use Lagrange multipliers to find the mini-mum distance from the curve or surface to the indicated point.[Hints: In Exercise 19, minimize subject to theconstraint In Exercise 25, use the root feature of agraphing utility.]
19. Recta:20. Recta:21. Recta:22. Recta:23. Parábola:24. Parábola:25. Parábola:26. Círculo:
27. Plano:28. Cono:
In Exercises 29 and 30, find the highest point on the curve ofintersection of the surfaces.
29. Cone: Plane:30. Sphere: Plane: 2x y z 2x2 y2 z2 36,
x 2z 4x2 y2 z2 0,
4, 0, 0z x2 y2
2, 1, 1x y z 1PuntoSuperficie0, 10x 4 2 y2 4
12, 1y x2 1
3, 0y x2
0, 3y x2
1, 0x 4y 30, 2x y 40, 02x 3y 10, 0x y 1PuntoCurva
x 1 y 1.f x, y x2 1 y2
x y 12x 2z 6,f x, y, z x2 y2 z2
x y z 0x y z 32,f x, y, z xyz
zy,x,f
f x, y e xy 4
f x, y x2 3xy y2
x2 1 y2 1.
x y 10f x, y x2 10x y 2 14y 28x y z 1
f x, y, z x2 y2 z2
x y z 3 0f x, y, z xyz
x y z 9 0f x, y, z x2 y2 z2
zy,x,
2x 4y 15 0f x, y x2 y2
x y 2 0f x, y 6 x2 y2
x2y 6f x, y 3x y 10
2x y 100f x, y 2x 2xy y2y x2 0f x, y x2 y2
x 2y 5 0f x, y x2 y2
yx
2
2−2
−2
c = 1c = 1
2
y
4
4
c = 2c = 4c = 6c = 8
−4
−4
y
2x 4y 5x y 4 0z x2 y2z x2 y2
2
2
4
4
6
6
c = 2c = 4c = 6
y
2
2
4
4
6
6
8
8
10
10
12
12c = 30c = 40c = 50
y
2x y 4x y 10z xyz xy
yx
1053714_1310.qxp 10/27/08 12:10 PM Page 976
976 Chapter 13 Functions of Several Variables
13.10 Exercises See www.CalcChat.com for worked-out solutions to odd-numbered exercises.
31. Explain what is meant by constrained optimizationproblems.
32. Explain the Method of Lagrange Multipliers for solvingconstrained optimization problems.
WRITING ABOUT CONCEPTS
In Exercises 1– 4, identify the constraint and level curves of theobjective function shown in the figure. Use the figure to approx-imate the indicated extrema, assuming that and are positive.Use Lagrange multipliers to verify your result.
1. Maximize 2. MaximizeConstraint: Constraint:
3. Minimize 4. MinimizeConstraint: Constraint:
In Exercises 5–10, use Lagrange multipliers to find the indicated extrema, assuming that and are positive.
5. MinimizeConstraint:
6. MaximizeConstraint:
7. MaximizeConstraint:
8. MinimizeConstraint:
9. MaximizeConstraint:
10. MinimizeConstraint:
In Exercises 11–14, use Lagrange multipliers to find theindicated extrema, assuming that and are positive.
11. MinimizarRestricción o ligadura:
12. MaximizarRestricción o ligadura:
13. MinimizarRestricción:
14. MinimizarRestricción:
In Exercises 15 and 16, use Lagrange multipliers to find anyextrema of the function subject to the constraint
15.
16.
In Exercises 17 and 18, use Lagrange multipliers to find theindicated extrema of subject to two constraints. In each case,assume that and are nonnegative.
17. MaximizeConstraints:
18. MinimizeConstraints:
In Exercises 19–28, use Lagrange multipliers to find the mini-mum distance from the curve or surface to the indicated point.[Hints: In Exercise 19, minimize subject to theconstraint In Exercise 25, use the root feature of agraphing utility.]
19. Recta:20. Recta:21. Recta:22. Recta:23. Parábola:24. Parábola:25. Parábola:26. Círculo:
27. Plano:28. Cono:
In Exercises 29 and 30, find the highest point on the curve ofintersection of the surfaces.
29. Cone: Plane:30. Sphere: Plane: 2x y z 2x2 y2 z2 36,
x 2z 4x2 y2 z2 0,
4, 0, 0z x2 y2
2, 1, 1x y z 1PuntoSuperficie0, 10x 4 2 y2 4
12, 1y x2 1
3, 0y x2
0, 3y x2
1, 0x 4y 30, 2x y 40, 02x 3y 10, 0x y 1PuntoCurva
x 1 y 1.f x, y x2 1 y2
x y 12x 2z 6,f x, y, z x2 y2 z2
x y z 0x y z 32,f x, y, z xyz
zy,x,f
f x, y e xy 4
f x, y x2 3xy y2
x2 1 y2 1.
x y 10f x, y x2 10x y 2 14y 28x y z 1
f x, y, z x2 y2 z2
x y z 3 0f x, y, z xyz
x y z 9 0f x, y, z x2 y2 z2
zy,x,
2x 4y 15 0f x, y x2 y2
x y 2 0f x, y 6 x2 y2
x2y 6f x, y 3x y 10
2x y 100f x, y 2x 2xy y2y x2 0f x, y x2 y2
x 2y 5 0f x, y x2 y2
yx
2
2−2
−2
c = 1c = 1
2
y
4
4
c = 2c = 4c = 6c = 8
−4
−4
y
2x 4y 5x y 4 0z x2 y2z x2 y2
2
2
4
4
6
6
c = 2c = 4c = 6
y
2
2
4
4
6
6
8
8
10
10
12
12c = 30c = 40c = 50
y
2x y 4x y 10z xyz xy
yx
1053714_1310.qxp 10/27/08 12:10 PM Page 976
976 Chapter 13 Functions of Several Variables
13.10 Exercises See www.CalcChat.com for worked-out solutions to odd-numbered exercises.
31. Explain what is meant by constrained optimizationproblems.
32. Explain the Method of Lagrange Multipliers for solvingconstrained optimization problems.
WRITING ABOUT CONCEPTS
In Exercises 1– 4, identify the constraint and level curves of theobjective function shown in the figure. Use the figure to approx-imate the indicated extrema, assuming that and are positive.Use Lagrange multipliers to verify your result.
1. Maximize 2. MaximizeConstraint: Constraint:
3. Minimize 4. MinimizeConstraint: Constraint:
In Exercises 5–10, use Lagrange multipliers to find the indicated extrema, assuming that and are positive.
5. MinimizeConstraint:
6. MaximizeConstraint:
7. MaximizeConstraint:
8. MinimizeConstraint:
9. MaximizeConstraint:
10. MinimizeConstraint:
In Exercises 11–14, use Lagrange multipliers to find theindicated extrema, assuming that and are positive.
11. MinimizarRestricción o ligadura:
12. MaximizarRestricción o ligadura:
13. MinimizarRestricción:
14. MinimizarRestricción:
In Exercises 15 and 16, use Lagrange multipliers to find anyextrema of the function subject to the constraint
15.
16.
In Exercises 17 and 18, use Lagrange multipliers to find theindicated extrema of subject to two constraints. In each case,assume that and are nonnegative.
17. MaximizeConstraints:
18. MinimizeConstraints:
In Exercises 19–28, use Lagrange multipliers to find the mini-mum distance from the curve or surface to the indicated point.[Hints: In Exercise 19, minimize subject to theconstraint In Exercise 25, use the root feature of agraphing utility.]
19. Recta:20. Recta:21. Recta:22. Recta:23. Parábola:24. Parábola:25. Parábola:26. Círculo:
27. Plano:28. Cono:
In Exercises 29 and 30, find the highest point on the curve ofintersection of the surfaces.
29. Cone: Plane:30. Sphere: Plane: 2x y z 2x2 y2 z2 36,
x 2z 4x2 y2 z2 0,
4, 0, 0z x2 y2
2, 1, 1x y z 1PuntoSuperficie0, 10x 4 2 y2 4
12, 1y x2 1
3, 0y x2
0, 3y x2
1, 0x 4y 30, 2x y 40, 02x 3y 10, 0x y 1PuntoCurva
x 1 y 1.f x, y x2 1 y2
x y 12x 2z 6,f x, y, z x2 y2 z2
x y z 0x y z 32,f x, y, z xyz
zy,x,f
f x, y e xy 4
f x, y x2 3xy y2
x2 1 y2 1.
x y 10f x, y x2 10x y 2 14y 28x y z 1
f x, y, z x2 y2 z2
x y z 3 0f x, y, z xyz
x y z 9 0f x, y, z x2 y2 z2
zy,x,
2x 4y 15 0f x, y x2 y2
x y 2 0f x, y 6 x2 y2
x2y 6f x, y 3x y 10
2x y 100f x, y 2x 2xy y2y x2 0f x, y x2 y2
x 2y 5 0f x, y x2 y2
yx
2
2−2
−2
c = 1c = 1
2
y
4
4
c = 2c = 4c = 6c = 8
−4
−4
y
2x 4y 5x y 4 0z x2 y2z x2 y2
2
2
4
4
6
6
c = 2c = 4c = 6
y
2
2
4
4
6
6
8
8
10
10
12
12c = 30c = 40c = 50
y
2x y 4x y 10z xyz xy
yx
1053714_1310.qxp 10/27/08 12:10 PM Page 976Larson-13-10.qxd 3/12/09 19:23 Page 976
966 CAPÍTULO 13 Funciones de varias variables
En los ejercicios 1 y 2, hallar la distancia mínima del punto alplano (Sugerencia: Para simplificar los cálcu-los, minimizar el cuadrado de la distancia.)
1. 2.
En los ejercicios 3 y 4, encontrar la distancia mínima desde elpunto a la superficie (Sugerencia: En elejercicio 4, usar la operación raíz de una herramienta de grafi-cación.)
En los ejercicios 5 a 8, hallar tres números positivos x, y y z quesatisfagan las condiciones dadas.
5. El producto es 27 y la suma es mínima.6. La suma es 32 y es máxima.7. La suma es 30 y la suma de los cuadrados es mínima.8. El producto es 1 y la suma de los cuadrados es mínima.
9. Costos Un contratista de mejorías caseras está pintando lasparedes y el techo de una habitación rectangular. El volumen dela habitación es de 668.25 pies cúbicos. El costo de pintura depared es de $0.06 por pie cuadrado y el costo de pintura de techoes de $0.11 por pie cuadrado. Encontrar las dimensiones de lahabitación que den por resultado un mínimo costo para la pintu-ra. ¿Cuál es el mínimo costo por la pintura?
10. Volumen máximo El material para construir la base de unacaja abierta cuesta 1.5 veces más por unidad de área que el mate-rial para construir los lados. Dada una cantidad fija de dinero C,hallar las dimensiones de la caja de mayor volumen que puedeser fabricada.
11. Volumen máximo El volumen de un elipsoide
es Dada una suma fija mostrar que el elip-soide de volumen máximo es una esfera.
a ! b ! c,4"abc!3.
x2
a2 !y 2
b2 !z2
c2 # 1
P ! xy2z
z ! !1 " 2x " 2y.
"1, 2, 3#"0, 0, 0#
x " y 1 z ! 3.
EJEMPLO 3 Hallar la recta de regresión de mínimos cuadrados
Hallar la recta de regresión de mínimos cuadrados para los puntos (!3, 0), (!1, 1), (0, 2)y (2, 3).
Solución La tabla muestra los cálculos necesarios para hallar la recta de regresión demínimos cuadrados usando
Aplicando el teorema 13.18 se obtiene
y
La recta de regresión de mínimos cuadrados es como se muestra en lafigura 13.77.
f "x# # 813x ! 47
26,
b #1n $%
n
i#1yi $ a%
n
i#1xi& #
14'6 $
813 "$2#( #
4726.
a #
n%n
i#1xiyi $ %
n
i#1xi %
n
i#1yi
n%n
i#1xi
2 $ $%n
i#1xi&2 #
4"5# $ "$2#"6#4"14# $ "$2#2 #
813
n # 4.
3
1
2
21−1−2−3x
(0, 2)
(2, 3)
47x + 268f(x) = 13
(−1, 1)(−3, 0)
y
Recta de regresión de mínimos cuadradosFigura 13.77
TECNOLOGÍA Muchas calcu-ladoras tienen “incorporados” pro-gramas de regresión de mínimoscuadrados. Se puede utilizar unacalculadora con estos programaspara reproducir los resultados delejemplo 3.
EXAMPLE 3 Finding the Least Squares Regression Line
Find the least squares regression line for the points and
Solution The table shows the calculations involved in finding the least squaresregression line using
Applying Theorem 13.18 produces
and
The least squares regression line is as shown in Figure 13.77.■
f "x# ! 813x " 47
26,
b !1n $%
n
i!1yi # a%
n
i!1xi& !
14'6 #
813 "#2#( !
4726.
a !
n%n
i!1xiyi # %
n
i!1xi %
n
i!1yi
n%n
i!1xi
2 # $%n
i!1xi&2 !
4"5# # "#2#"6#4"14# # "#2#2 !
813
n ! 4.
"2, 3#."#3, 0#, "#1, 1#, "0, 2#,
966 Chapter 13 Functions of Several Variables
In Exercises 1 and 2, find the minimum distance from the pointto the plane (Hint: To simplify the computations,minimize the square of the distance.)
1. 2.
In Exercises 3 and 4, find the minimum distance from the pointto the surface (Hint: In Exercise 4, use theroot feature of a graphing utility.)
3.
4.
In Exercises 5–8, find three positive integers and thatsatisfy the given conditions.
5. The product is 27 and the sum is a minimum.6. The sum is 32 and is a maximum.7. The sum is 30 and the sum of the squares is a minimum.8. The product is 1 and the sum of the squares is a minimum.
9. Cost A home improvement contractor is painting the wallsand ceiling of a rectangular room. The volume of the room is668.25 cubic feet. The cost of wall paint is $0.06 per squarefoot and the cost of ceiling paint is $0.11 per square foot. Findthe room dimensions that result in a minimum cost for thepaint. What is the minimum cost for the paint?
10. Maximum Volume The material for constructing the baseof an open box costs 1.5 times as much per unit area as thematerial for constructing the sides. For a fixed amount ofmoney find the dimensions of the box of largest volume thatcan be made.
11. Maximum Volume The volume of an ellipsoid
is For a fixed sum show that the ellipsoidof maximum volume is a sphere.
a " b " c,4$abc)3.
x2
a2 "y 2
b2 "z2
c2 ! 1
C,
P ! xy2z
zy,x,
"0, 0, 2#"#2, #2, 0#
z ! !1 " 2x " 2y.
"1, 2, 3#"0, 0, 0#
x " y 1 z ! 3.
13.9 Exercises See www.CalcChat.com for worked-out solutions to odd-numbered exercises.
Many calculatorshave “built-in” least squares regressionprograms. If your calculator has such aprogram, use it to duplicate the resultsof Example 3.
TECHNOLOGY
3
1
2
21−1−2−3x
(0, 2)
(2, 3)
x +813f(x) = 47
26
(−1, 1)(−3, 0)
y
Least squares regression lineFigure 13.77
x y xy x2
#3 0 0 9
#1 1 #1 1
0 2 0 0
2 3 6 4
%n
i!1xi ! #2 %
n
i!1yi ! 6 %
n
i!1xiyi ! 5 %
n
i!1xi
2 ! 14
1053714_1309.qxp 10/27/08 12:10 PM Page 966
EXAMPLE 3 Finding the Least Squares Regression Line
Find the least squares regression line for the points and
Solution The table shows the calculations involved in finding the least squaresregression line using
Applying Theorem 13.18 produces
and
The least squares regression line is as shown in Figure 13.77.■
f "x# ! 813x " 47
26,
b !1n $%
n
i!1yi # a%
n
i!1xi& !
14'6 #
813 "#2#( !
4726.
a !
n%n
i!1xiyi # %
n
i!1xi %
n
i!1yi
n%n
i!1xi
2 # $%n
i!1xi&2 !
4"5# # "#2#"6#4"14# # "#2#2 !
813
n ! 4.
"2, 3#."#3, 0#, "#1, 1#, "0, 2#,
966 Chapter 13 Functions of Several Variables
In Exercises 1 and 2, find the minimum distance from the pointto the plane (Hint: To simplify the computations,minimize the square of the distance.)
1. 2.
In Exercises 3 and 4, find the minimum distance from the pointto the surface (Hint: In Exercise 4, use theroot feature of a graphing utility.)
3.
4.
In Exercises 5–8, find three positive integers and thatsatisfy the given conditions.
5. The product is 27 and the sum is a minimum.6. The sum is 32 and is a maximum.7. The sum is 30 and the sum of the squares is a minimum.8. The product is 1 and the sum of the squares is a minimum.
9. Cost A home improvement contractor is painting the wallsand ceiling of a rectangular room. The volume of the room is668.25 cubic feet. The cost of wall paint is $0.06 per squarefoot and the cost of ceiling paint is $0.11 per square foot. Findthe room dimensions that result in a minimum cost for thepaint. What is the minimum cost for the paint?
10. Maximum Volume The material for constructing the baseof an open box costs 1.5 times as much per unit area as thematerial for constructing the sides. For a fixed amount ofmoney find the dimensions of the box of largest volume thatcan be made.
11. Maximum Volume The volume of an ellipsoid
is For a fixed sum show that the ellipsoidof maximum volume is a sphere.
a " b " c,4$abc)3.
x2
a2 "y 2
b2 "z2
c2 ! 1
C,
P ! xy2z
zy,x,
"0, 0, 2#"#2, #2, 0#
z ! !1 " 2x " 2y.
"1, 2, 3#"0, 0, 0#
x " y 1 z ! 3.
13.9 Exercises See www.CalcChat.com for worked-out solutions to odd-numbered exercises.
Many calculatorshave “built-in” least squares regressionprograms. If your calculator has such aprogram, use it to duplicate the resultsof Example 3.
TECHNOLOGY
3
1
2
21−1−2−3x
(0, 2)
(2, 3)
x +813f(x) = 47
26
(−1, 1)(−3, 0)
y
Least squares regression lineFigure 13.77
x y xy x2
#3 0 0 9
#1 1 #1 1
0 2 0 0
2 3 6 4
%n
i!1xi ! #2 %
n
i!1yi ! 6 %
n
i!1xiyi ! 5 %
n
i!1xi
2 ! 14
1053714_1309.qxp 10/27/08 12:10 PM Page 966
13.9 Ejercicios
Larson-13-09.qxd 3/12/09 19:18 Page 966
SECCIÓN 13.9 Aplicaciones de los extremos de funciones de dos variables 967
12. Volumen máximo Mostrar que la caja rectangular de volumenmáximo inscrita en una esfera de radio r es un cubo.
13. Volumen y área exterior Mostrar que una caja rectangular devolumen dado y área exterior mínima es un cubo.
14. Área Un comedero de secciones transversales en forma detrapecio se forma doblando los extremos de una lámina de alu-minio de 30 pulgadas de ancho (ver la figura). Hallar la seccióntransversal de área máxima.
15. Ingreso máximo Una empresa fabrica dos tipos de zapatostenis, tenis para correr y tenis para baloncesto. El ingreso total de
unidades de tenis para correr y unidades de tenis de balon-cesto es donde y están en miles de unidades. Hallar las y que maximizanel ingreso.
16. Ganancia o beneficio máximo Una empresa fabrica velas endos lugares. El costo de producción de unidades en el lugar 1es
y el costo de producción de x2 unidades en el lugar 2 es
Las velas se venden a $15 por unidad. Hallar la cantidad quedebe producirse en cada lugar para aumentar al máximo el be-neficio
17. Ley de Hardy-Weinberg Los tipos sanguíneos son genética-mente determinados por tres alelos A, B y O. (Alelo escualquiera de las posibles formas de mutación de un gen.) Unapersona cuyo tipo sanguíneo es AA, BB u OO es homocigótica.Una persona cuyo tipo sanguíneo es AB, AO o BO es hetero-cigótica. La ley Hardy-Weinberg establece que la proporción Pde individuos heterocigótica en cualquier población dada es
donde p representa el porcentaje de alelos A en la población, qrepresenta el porcentaje de alelos B en la población y r repre-senta el porcentaje de alelos O en la población. Utilizar el hechode que para mostrar que la proporción máxi-ma de individuos heterocigóticos en cualquier población es
18. Índice de diversidad de Shannon Una forma de medir diversi-dad de especies es usar el índice de diversidad de Shannon H. Siun hábitat consiste de tres especies, A, B y C, su índice de diver-sidad de Shannon es
donde x es el porcentaje de especies A en el hábitat, y es el por-centaje de especies B en el hábitat y z es el porcentaje deespecies C en el hábitat.a) Usar el factor de x + y + z = 1 para demostrar que el valor
máximo de H ocurre cuando b) Usar el resultado del inciso a) para demostrar que el valor
máximo de H en este hábitat es de ln 3.
19. Costo mínimo Hay que construir un conducto para agua desdeel punto P al punto S y debe atravesar regiones donde los costosde construcción difieren (ver la figura). El costo por kilómetroen dólares es 3k de P a Q, 2k de Q a R y k de R a S. Hallar x y ytales que el costo total C se minimice.
20. Distancia Una empresa tiene tres tiendas de ventas al menudeolocalizadas en los puntos (0, 0), (2, 2) y (!2, 2) (ver la figura). Ladirección planea construir un centro de distribución localizado detal manera que la suma S de las distancias del centro a las tiendassea mínimo. Por la simetría del problema es claro que el centro dedistribución se localizará en el eje y, y por consiguiente S es unafunción de una variable y. Utilizando las técnicas presentadas en elcapítulo 3, calcular el valor de y requerido.
Figura para 20 Figura para 21
21. Investigación Las tiendas de ventas al menudeo descritas en elejercicio 20 se localizan en (0, 0), (4, 2) y (!2, 2) (ver la figura).La localización del centro de distribución es (x, y), y por consi-guiente la suma S de las distancias es una función de x y y.a) Escribir la expresión que da la suma S de las distancias.
Utilizar un sistema algebraico por computadora y representarS. ¿Tiene esta superficie un mínimo?
b) Utilizar un sistema algebraico por computadora y obtener y Observar que resolver el sistema y es muydifícil. Por tanto, aproximar la localización del centro de dis-tribución.
c) Una estimación inicial del punto crítico es Calcular con componentes y ¿Qué dirección es la dada por el vector
d) La segunda estimación del punto crítico es
Si se sustituyen estas coordenadas en entonces S seconvierte en una función de una variable t. Hallar el valor det que minimiza S. Utilizar este valor de t para estimar
e) Realizar dos iteraciones más del proceso del inciso d) paraobtener Dada esta localización del centro de dis-tribución, ¿cuál es la suma de las distancias a las tiendas almenudeo?
f) Explicar por qué se usó para aproximar el valormínimo de S. ¿En qué tipo de problemas se usaría !S!x, y"?
"!S!x, y"
!x4, y4".
!x2, y2".
S!x, y",!x2, y2" # !x1 " Sx!x1, y1"t, y1 " Sy!x1, y1"t".
"!S!1, 1"?"Sy!1, 1"."Sx!1, 1""!S!1, 1"
!x1, y1" # !1, 1".
Sy # 0Sx # 0Sy.Sx
x2 4
4
−2
−2
(−2, 2) (4, 2)
(0, 0)
(x, y)d1 d2
d3
y
x−3
−2
−2
3
2
21
(2, 2)(−2, 2)
(0, y)d1
d2
d3
(0, 0)
y
1 km
P
Q
R
S
x
y
10 km
2 km
12. Maximum Volume Show that the rectangular box of maxi-mum volume inscribed in a sphere of radius is a cube.
13. Volume and Surface Area Show that a rectangular box ofgiven volume and minimum surface area is a cube.
14. Area A trough with trapezoidal cross sections is formed byturning up the edges of a 30-inch-wide sheet of aluminum (seefigure). Find the cross section of maximum area.
15. Maximum Revenue A company manufactures two types ofsneakers, running shoes and basketball shoes. The total revenuefrom units of running shoes and units of basketball shoesis where and
are in thousands of units. Find and so as to maximizethe revenue.
16. Maximum Profit A corporation manufactures candles at twolocations. The cost of producing units at location 1 is
and the cost of producing units at location 2 is
The candles sell for $15 per unit. Find the quantity that shouldbe produced at each location to maximize the profit
17. Hardy-Weinberg Law Common blood types are determinedgenetically by three alleles A, B, and O. (An allele is any of agroup of possible mutational forms of a gene.) A person whoseblood type is AA, BB, or OO is homozygous. A person whoseblood type is AB, AO, or BO is heterozygous. The Hardy-Weinberg Law states that the proportion of heterozygousindividuals in any given population is
where represents the percent of allele A in the population,represents the percent of allele B in the population, and represents the percent of allele O in the population. Use the factthat to show that the maximum proportion ofheterozygous individuals in any population is
18. Shannon Diversity Index One way to measure species diver-sity is to use the Shannon diversity index If a habitat consistsof three species, A, B, and C, its Shannon diversity index is
where is the percent of species A in the habitat, is the percent of species B in the habitat, and is the percent ofspecies C in the habitat.(a) Use the fact that to show that the maximum
value of occurs when (b) Use the results of part (a) to show that the maximum value
of in this habitat is
19. Minimum Cost A water line is to be built from point topoint and must pass through regions where construction costsdiffer (see figure). The cost per kilometer in dollars is from
to from to and from to Find and suchthat the total cost will be minimized.
20. Distance A company has retail outlets located at the pointsand (see figure). Management plans to
build a distribution center located such that the sum of thedistances from the center to the outlets is minimum. From thesymmetry of the problem it is clear that the distribution centerwill be located on the axis, and therefore is a function of thesingle variable Using techniques presented in Chapter 3, findthe required value of
Figure for 20 Figure for 21
21. Investigation The retail outlets described in Exercise 20 arelocated at and (see figure). The locationof the distribution center is and therefore the sum of thedistances is a function of and (a) Write the expression giving the sum of the distances Use
a computer algebra system to graph Does the surfacehave a minimum?
(b) Use a computer algebra system to obtain and Observethat solving the system and is very difficult.So, approximate the location of the distribution center.
(c) An initial estimate of the critical point is Calculate with components and
What direction is given by the vector (d) The second estimate of the critical point is
If these coordinates are substituted into then becomes a function of the single variable Find the valueof that minimizes Use this value of to estimate
(e) Complete two more iterations of the process in part (d) toobtain For this location of the distribution center,what is the sum of the distances to the retail outlets?
(f) Explain why was used to approximate theminimum value of In what types of problems would youuse S x, y ?
S.S x, y
x4, y4 .
x2, y2 .tS.tt.
SS x, y ,
x2, y2 x1 Sx x1, y1 t, y1 Sy x1, y1 t .
S 1, 1 ?Sy 1, 1 .Sx 1, 1S 1, 1
x1, y1 1, 1 .
Sy 0Sx 0Sy.Sx
S.S.
y.xSx, y ,
2, 24, 2 ,0, 0 ,
2 4
4
−2
−2
(−2, 2) (4, 2)
(0, 0)
(x, y)d2 d1
d3
y
−3
−2
−2
32
21
(2, 2)(−2, 2)
(0, y)d1
d2
d3
(0, 0)
y
y.y.
Sy-
S
2, 22, 2 ,0, 0 ,
1 km
P
Q
R
S
x
y
10 km
2 km
CyxS.RkR,Q2kQ,P
3kS
P
ln 3.H
x y z 13.H
x y z 1
zyx
H x ln x y ln y z ln z
H.
23.
p q r 1
rqp
P p, q, r 2pq 2pr 2qr
P
P 15 x1 x2 C1 C2.
C2 0.05x22 4x2 275.
x2
C1 0.02x12 4x1 500
x1
x2x1x2
x1R 5x12 8x2
2 2x1x2 42x1 102x2,x2x1
30 − 2x
x x
θθ
r
13.9 Applications of Extrema of Functions of Two Variables 967
CAS
1053714_1309.qxp 10/27/08 12:10 PM Page 967
23.
p $ q $ r # 1
P! p, q, r" # 2pq $ 2pr $ 2qr
P # 15!x1 $ x2" " C1 " C2.
C2 # 0.05x22 $ 4x2 $ 275.
C1 # 0.02x12 $ 4x1 $ 500
x1
x2x1x2
x1R # "5x12 " 8x2
2 " 2x1x2 $ 42x1 $ 102x2,x2x1
30 − 2x
x x
θθ
12. Maximum Volume Show that the rectangular box of maxi-mum volume inscribed in a sphere of radius is a cube.
13. Volume and Surface Area Show that a rectangular box ofgiven volume and minimum surface area is a cube.
14. Area A trough with trapezoidal cross sections is formed byturning up the edges of a 30-inch-wide sheet of aluminum (seefigure). Find the cross section of maximum area.
15. Maximum Revenue A company manufactures two types ofsneakers, running shoes and basketball shoes. The total revenuefrom units of running shoes and units of basketball shoesis where and
are in thousands of units. Find and so as to maximizethe revenue.
16. Maximum Profit A corporation manufactures candles at twolocations. The cost of producing units at location 1 is
and the cost of producing units at location 2 is
The candles sell for $15 per unit. Find the quantity that shouldbe produced at each location to maximize the profit
17. Hardy-Weinberg Law Common blood types are determinedgenetically by three alleles A, B, and O. (An allele is any of agroup of possible mutational forms of a gene.) A person whoseblood type is AA, BB, or OO is homozygous. A person whoseblood type is AB, AO, or BO is heterozygous. The Hardy-Weinberg Law states that the proportion of heterozygousindividuals in any given population is
where represents the percent of allele A in the population,represents the percent of allele B in the population, and represents the percent of allele O in the population. Use the factthat to show that the maximum proportion ofheterozygous individuals in any population is
18. Shannon Diversity Index One way to measure species diver-sity is to use the Shannon diversity index If a habitat consistsof three species, A, B, and C, its Shannon diversity index is
where is the percent of species A in the habitat, is the percent of species B in the habitat, and is the percent ofspecies C in the habitat.(a) Use the fact that to show that the maximum
value of occurs when (b) Use the results of part (a) to show that the maximum value
of in this habitat is
19. Minimum Cost A water line is to be built from point topoint and must pass through regions where construction costsdiffer (see figure). The cost per kilometer in dollars is from
to from to and from to Find and suchthat the total cost will be minimized.
20. Distance A company has retail outlets located at the pointsand (see figure). Management plans to
build a distribution center located such that the sum of thedistances from the center to the outlets is minimum. From thesymmetry of the problem it is clear that the distribution centerwill be located on the axis, and therefore is a function of thesingle variable Using techniques presented in Chapter 3, findthe required value of
Figure for 20 Figure for 21
21. Investigation The retail outlets described in Exercise 20 arelocated at and (see figure). The locationof the distribution center is and therefore the sum of thedistances is a function of and (a) Write the expression giving the sum of the distances Use
a computer algebra system to graph Does the surfacehave a minimum?
(b) Use a computer algebra system to obtain and Observethat solving the system and is very difficult.So, approximate the location of the distribution center.
(c) An initial estimate of the critical point is Calculate with components and
What direction is given by the vector (d) The second estimate of the critical point is
If these coordinates are substituted into then becomes a function of the single variable Find the valueof that minimizes Use this value of to estimate
(e) Complete two more iterations of the process in part (d) toobtain For this location of the distribution center,what is the sum of the distances to the retail outlets?
(f) Explain why was used to approximate theminimum value of In what types of problems would youuse S x, y ?
S.S x, y
x4, y4 .
x2, y2 .tS.tt.
SS x, y ,
x2, y2 x1 Sx x1, y1 t, y1 Sy x1, y1 t .
S 1, 1 ?Sy 1, 1 .Sx 1, 1S 1, 1
x1, y1 1, 1 .
Sy 0Sx 0Sy.Sx
S.S.
y.xSx, y ,
2, 24, 2 ,0, 0 ,
2 4
4
−2
−2
(−2, 2) (4, 2)
(0, 0)
(x, y)d2 d1
d3
y
−3
−2
−2
32
21
(2, 2)(−2, 2)
(0, y)d1
d2
d3
(0, 0)
y
y.y.
Sy-
S
2, 22, 2 ,0, 0 ,
1 km
P
Q
R
S
x
y
10 km
2 km
CyxS.RkR,Q2kQ,P
3kS
P
ln 3.H
x y z 13.H
x y z 1
zyx
H x ln x y ln y z ln z
H.
23.
p q r 1
rqp
P p, q, r 2pq 2pr 2qr
P
P 15 x1 x2 C1 C2.
C2 0.05x22 4x2 275.
x2
C1 0.02x12 4x1 500
x1
x2x1x2
x1R 5x12 8x2
2 2x1x2 42x1 102x2,x2x1
30 − 2x
x x
θθ
r
13.9 Applications of Extrema of Functions of Two Variables 967
CAS
1053714_1309.qxp 10/27/08 12:10 PM Page 967
12. Maximum Volume Show that the rectangular box of maxi-mum volume inscribed in a sphere of radius is a cube.
13. Volume and Surface Area Show that a rectangular box ofgiven volume and minimum surface area is a cube.
14. Area A trough with trapezoidal cross sections is formed byturning up the edges of a 30-inch-wide sheet of aluminum (seefigure). Find the cross section of maximum area.
15. Maximum Revenue A company manufactures two types ofsneakers, running shoes and basketball shoes. The total revenuefrom units of running shoes and units of basketball shoesis where and
are in thousands of units. Find and so as to maximizethe revenue.
16. Maximum Profit A corporation manufactures candles at twolocations. The cost of producing units at location 1 is
and the cost of producing units at location 2 is
The candles sell for $15 per unit. Find the quantity that shouldbe produced at each location to maximize the profit
17. Hardy-Weinberg Law Common blood types are determinedgenetically by three alleles A, B, and O. (An allele is any of agroup of possible mutational forms of a gene.) A person whoseblood type is AA, BB, or OO is homozygous. A person whoseblood type is AB, AO, or BO is heterozygous. The Hardy-Weinberg Law states that the proportion of heterozygousindividuals in any given population is
where represents the percent of allele A in the population,represents the percent of allele B in the population, and represents the percent of allele O in the population. Use the factthat to show that the maximum proportion ofheterozygous individuals in any population is
18. Shannon Diversity Index One way to measure species diver-sity is to use the Shannon diversity index If a habitat consistsof three species, A, B, and C, its Shannon diversity index is
where is the percent of species A in the habitat, is the percent of species B in the habitat, and is the percent ofspecies C in the habitat.(a) Use the fact that to show that the maximum
value of occurs when (b) Use the results of part (a) to show that the maximum value
of in this habitat is
19. Minimum Cost A water line is to be built from point topoint and must pass through regions where construction costsdiffer (see figure). The cost per kilometer in dollars is from
to from to and from to Find and suchthat the total cost will be minimized.
20. Distance A company has retail outlets located at the pointsand (see figure). Management plans to
build a distribution center located such that the sum of thedistances from the center to the outlets is minimum. From thesymmetry of the problem it is clear that the distribution centerwill be located on the axis, and therefore is a function of thesingle variable Using techniques presented in Chapter 3, findthe required value of
Figure for 20 Figure for 21
21. Investigation The retail outlets described in Exercise 20 arelocated at and (see figure). The locationof the distribution center is and therefore the sum of thedistances is a function of and (a) Write the expression giving the sum of the distances Use
a computer algebra system to graph Does the surfacehave a minimum?
(b) Use a computer algebra system to obtain and Observethat solving the system and is very difficult.So, approximate the location of the distribution center.
(c) An initial estimate of the critical point is Calculate with components and
What direction is given by the vector (d) The second estimate of the critical point is
If these coordinates are substituted into then becomes a function of the single variable Find the valueof that minimizes Use this value of to estimate
(e) Complete two more iterations of the process in part (d) toobtain For this location of the distribution center,what is the sum of the distances to the retail outlets?
(f) Explain why was used to approximate theminimum value of In what types of problems would youuse S x, y ?
S.S x, y
x4, y4 .
x2, y2 .tS.tt.
SS x, y ,
x2, y2 x1 Sx x1, y1 t, y1 Sy x1, y1 t .
S 1, 1 ?Sy 1, 1 .Sx 1, 1S 1, 1
x1, y1 1, 1 .
Sy 0Sx 0Sy.Sx
S.S.
y.xSx, y ,
2, 24, 2 ,0, 0 ,
2 4
4
−2
−2
(−2, 2) (4, 2)
(0, 0)
(x, y)d2 d1
d3
y
−3
−2
−2
32
21
(2, 2)(−2, 2)
(0, y)d1
d2
d3
(0, 0)
y
y.y.
Sy-
S
2, 22, 2 ,0, 0 ,
1 km
P
Q
R
S
x
y
10 km
2 km
CyxS.RkR,Q2kQ,P
3kS
P
ln 3.H
x y z 13.H
x y z 1
zyx
H x ln x y ln y z ln z
H.
23.
p q r 1
rqp
P p, q, r 2pq 2pr 2qr
P
P 15 x1 x2 C1 C2.
C2 0.05x22 4x2 275.
x2
C1 0.02x12 4x1 500
x1
x2x1x2
x1R 5x12 8x2
2 2x1x2 42x1 102x2,x2x1
30 − 2x
x x
θθ
r
13.9 Applications of Extrema of Functions of Two Variables 967
CAS
1053714_1309.qxp 10/27/08 12:10 PM Page 967
Larson-13-09.qxd 3/12/09 19:18 Page 967
SECCIÓN 13.10 Multiplicadores de Lagrange 977
En los ejercicios 33 a 42, usar los multiplicadores de Lagrangepara resolver el ejercicio indicado en la sección 13.9.33. Ejercicio 1 34. Ejercicio 235. Ejercicio 5 36. Ejercicio 637. Ejercicio 9 38. Ejercicio 1039. Ejercicio 11 40. Ejercicio 1241. Ejercicio 17 42. Ejercicio 18
43. Volumen máximo Utilizar multiplicadores de Lagrange para de-terminar las dimensiones de la caja rectangular de volumen máxi-mo que puede ser inscrita (con los bordes paralelos a los ejes decoordenadas) en el elipsoide
45. Costo mínimo Un contenedor de carga (en forma de un sólidorectangular) debe tener un volumen de 480 pies cúbicos. Laparte inferior costará $5 por pie cuadrado para construir, y loslados y la parte superior costarán $3 por pie cuadrado para cons-trucción. Usar los multiplicadores de Lagrange para encontrarlas dimensiones del contenedor de este tamaño que tiene costomínimo.
46. Medias geométrica y aritméticaa) Utilizar los multiplicadores de Lagrange para demostrar que
el producto de tres números positivos x, y y z cuya suma tieneun valor constante S, es máximo cuando los tres números soniguales. Utilizar este resultado para demostrar que
b) Generalizar el resultado del inciso a) para demostrar que elproducto es máximo cuando
y todo Después, demostrar que
Esto demuestra que la media geométrica nunca es mayorque la media aritmética.
47. Superficie mínima Utilizar multiplicadores de Lagrange paraencontrar las dimensiones de un cilindro circular recto con vo-lumen de V0 unidades cúbicas y superficie mínima.
48. Distribución de temperatura Sea la temperatura en cada punto sobre la esfera x2 ! y2 ! z2
" 50. Hallar la temperatura máxima en la curva formada por laintersección de la esfera y el plano
49. Refracción de la luz Cuando las ondas de luz que viajan en unmedio transparente atraviesan la superficie de un segundo mediotransparente, tienden a “desviarse” para seguir la trayectoria detiempo mínimo. Esta tendencia se llama refracción y está descri-ta por la ley de refracción de Snell, según la cual
donde y son las magnitudes de los ángulos mostrados en lafigura, y y son las velocidades de la luz en los dos medios.Utilizar los multiplicadores de Lagrange para deducir esta leyusando
Figura para 49 Figura para 50
50. Área y perímetro Un semicírculo está sobre un rectángulo (verla figura). Si el área es fija y el perímetro es un mínimo, o si elperímetro es fijo y el área es un máximo, utilizar multiplicadoresde Lagrange para verificar que la longitud del rectángulo es eldoble de su altura.
Nivel de producción En los ejercicios 51 y 52, hallar el máximonivel de producción P si el costo total de trabajo (a $72 porunidad) y capital (a $60 por unidad) está restringido a $250 000,donde x es el número de unidades de trabajo y y es el número deunidades de capital.
51. 52.
Costo En los ejercicios 53 y 54, hallar el costo mínimo para pro-ducir 50 000 unidades de un producto donde x es el número deunidades de trabajo (a $72 por unidad) y y es el número de uni-dades de capital (a $60 por unidad).
53. 54.
55. Investigación Considerar la función objetivo sujeta a la restricción o ligadura de que #, $
y % sean los ángulos de un triángulo.a) Utilizar los multiplicadores de Lagrange para maximizar b) Utilizar la restricción o ligadura para reducir la función g a
una función de dos variables independientes. Utilizar un sis-tema algebraico por computadora para representar gráfica-mente la superficie definida por g. Identificar en la gráfica losvalores máximos.
g.
In Exercises 33–42, use Lagrange multipliers to solve the indi-cated exercise in Section 13.9.
33. Exercise 1 34. Exercise 235. Exercise 5 36. Exercise 637. Exercise 9 38. Exercise 1039. Exercise 11 40. Exercise 1241. Exercise 17 42. Exercise 18
43. Maximum Volume Use Lagrange multipliers to find thedimensions of a rectangular box of maximum volume that canbe inscribed (with edges parallel to the coordinate axes) in theellipsoid
45. Minimum Cost A cargo container (in the shape of a rectangularsolid) must have a volume of 480 cubic feet. The bottom willcost $5 per square foot to construct and the sides and the topwill cost $3 per square foot to construct. Use Lagrangemultipliers to find the dimensions of the container of this sizethat has minimum cost.
46. Geometric and Arithmetic Means(a) Use Lagrange multipliers to prove that the product of three
positive numbers and whose sum has the constantvalue is a maximum when the three numbers are equal.Use this result to prove that
(b) Generalize the result of part (a) to prove that the productis a maximum when
and all Then prove that
This shows that the geometric mean is never greater thanthe arithmetic mean.
47. Minimum Surface Area Use Lagrange multipliers to find thedimensions of a right circular cylinder with volume cubicunits and minimum surface area.
48. Temperature Distribution Letrepresent the temperature at each point on the sphere
Find the maximum temperature on thecurve formed by the intersection of the sphere and the plane
49. Refraction of Light When light waves traveling in atransparent medium strike the surface of a second transparentmedium, they tend to “bend” in order to follow the path ofminimum time. This tendency is called refraction and isdescribed by Snell’s Law of Refraction,
where and are the magnitudes of the angles shown in thefigure, and and are the velocities of light in the two media.Use Lagrange multipliers to derive this law using
Figure for 49 Figure for 50
50. Area and Perimeter A semicircle is on top of a rectangle (seefigure). If the area is fixed and the perimeter is a minimum, orif the perimeter is fixed and the area is a maximum, useLagrange multipliers to verify that the length of the rectangle istwice its height.
Production Level In Exercises 51 and 52, find the maximumproduction level if the total cost of labor (at $72 per unit) andcapital (at $60 per unit) is limited to $250,000, where is thenumber of units of labor and is the number of units of capital.
51. 52.
Cost In Exercises 53 and 54, find the minimum cost ofproducing 50,000 units of a product, where is the numberof units of labor (at $72 per unit) and is the number of units ofcapital (at $60 per unit).
53. 54.
55. Investigation Consider the objective function subject to the constraint that , and are
the angles of a triangle.(a) Use Lagrange multipliers to maximize (b) Use the constraint to reduce the function to a function of
two independent variables. Use a computer algebra systemto graph the surface represented by Identify themaximum values on the graph.
g.
gg.
,cos cos cosg , ,
P x, y 100x0.6y0.4P x, y 100x0.25y0.75
yx
P x, y 100x0.4y0.6P x, y 100x0.25y0.75
yx
P
l
h
a
x
d1
y1θ
2θQ
d2
Medium 1
Medium 2
Px y a.
v2v1
21
sin 1
v1
sin 2
v2
x z 0.
x2 y2 z2 50.
T x, y, z 100 x2 y2
V0
n x1x2x3. . . xn
x1 x2 x3. . . xn
n .
xi 0.. . . xn,n
i 1xi S,
x1 x2 x3x1x2x3. . . xn
3 xyz x y z 3.S,
z,y,x,
x2 a2 y2 b2 z2 c2 1.
13.10 Lagrange Multipliers 977
44. The sum of the length and the girth (perimeter of a crosssection) of a package carried by a delivery service cannotexceed 108 inches.(a) Determine whether Lagrange multipliers can be used to
find the dimensions of the rectangular package oflargest volume that may be sent. Explain your reasoning.
(b) If Lagrange multipliers can be used, find the dimen-sions. Compare your answer with that obtained inExercise 38, Section 13.9.
CAPSTONE
CAS
56. A can buoy is to be made of three pieces, namely, a cylinderand two equal cones, the altitude of each cone being equalto the altitude of the cylinder. For a given area of surface, what shape will have the greatest volume?
This problem was composed by the Committee on the Putnam Prize Competition.© The Mathematical Association of America. All rights reserved.
PUTNAM EXAM CHALLENGE
1053714_1310.qxp 10/27/08 12:10 PM Page 977
In Exercises 33–42, use Lagrange multipliers to solve the indi-cated exercise in Section 13.9.
33. Exercise 1 34. Exercise 235. Exercise 5 36. Exercise 637. Exercise 9 38. Exercise 1039. Exercise 11 40. Exercise 1241. Exercise 17 42. Exercise 18
43. Maximum Volume Use Lagrange multipliers to find thedimensions of a rectangular box of maximum volume that canbe inscribed (with edges parallel to the coordinate axes) in theellipsoid
45. Minimum Cost A cargo container (in the shape of a rectangularsolid) must have a volume of 480 cubic feet. The bottom willcost $5 per square foot to construct and the sides and the topwill cost $3 per square foot to construct. Use Lagrangemultipliers to find the dimensions of the container of this sizethat has minimum cost.
46. Geometric and Arithmetic Means(a) Use Lagrange multipliers to prove that the product of three
positive numbers and whose sum has the constantvalue is a maximum when the three numbers are equal.Use this result to prove that
(b) Generalize the result of part (a) to prove that the productis a maximum when
and all Then prove that
This shows that the geometric mean is never greater thanthe arithmetic mean.
47. Minimum Surface Area Use Lagrange multipliers to find thedimensions of a right circular cylinder with volume cubicunits and minimum surface area.
48. Temperature Distribution Letrepresent the temperature at each point on the sphere
Find the maximum temperature on thecurve formed by the intersection of the sphere and the plane
49. Refraction of Light When light waves traveling in atransparent medium strike the surface of a second transparentmedium, they tend to “bend” in order to follow the path ofminimum time. This tendency is called refraction and isdescribed by Snell’s Law of Refraction,
where and are the magnitudes of the angles shown in thefigure, and and are the velocities of light in the two media.Use Lagrange multipliers to derive this law using
Figure for 49 Figure for 50
50. Area and Perimeter A semicircle is on top of a rectangle (seefigure). If the area is fixed and the perimeter is a minimum, orif the perimeter is fixed and the area is a maximum, useLagrange multipliers to verify that the length of the rectangle istwice its height.
Production Level In Exercises 51 and 52, find the maximumproduction level if the total cost of labor (at $72 per unit) andcapital (at $60 per unit) is limited to $250,000, where is thenumber of units of labor and is the number of units of capital.
51. 52.
Cost In Exercises 53 and 54, find the minimum cost ofproducing 50,000 units of a product, where is the numberof units of labor (at $72 per unit) and is the number of units ofcapital (at $60 per unit).
53. 54.
55. Investigation Consider the objective function subject to the constraint that , and are
the angles of a triangle.(a) Use Lagrange multipliers to maximize (b) Use the constraint to reduce the function to a function of
two independent variables. Use a computer algebra systemto graph the surface represented by Identify themaximum values on the graph.
g.
gg.
,cos cos cosg , ,
P x, y 100x0.6y0.4P x, y 100x0.25y0.75
yx
P x, y 100x0.4y0.6P x, y 100x0.25y0.75
yx
P
l
h
a
x
d1
y1θ
2θQ
d2
Medium 1
Medium 2
Px y a.
v2v1
21
sin 1
v1
sin 2
v2
x z 0.
x2 y2 z2 50.
T x, y, z 100 x2 y2
V0
n x1x2x3. . . xn
x1 x2 x3. . . xn
n .
xi 0.. . . xn,n
i 1xi S,
x1 x2 x3x1x2x3. . . xn
3 xyz x y z 3.S,
z,y,x,
x2 a2 y2 b2 z2 c2 1.
13.10 Lagrange Multipliers 977
44. The sum of the length and the girth (perimeter of a crosssection) of a package carried by a delivery service cannotexceed 108 inches.(a) Determine whether Lagrange multipliers can be used to
find the dimensions of the rectangular package oflargest volume that may be sent. Explain your reasoning.
(b) If Lagrange multipliers can be used, find the dimen-sions. Compare your answer with that obtained inExercise 38, Section 13.9.
CAPSTONE
CAS
56. A can buoy is to be made of three pieces, namely, a cylinderand two equal cones, the altitude of each cone being equalto the altitude of the cylinder. For a given area of surface, what shape will have the greatest volume?
This problem was composed by the Committee on the Putnam Prize Competition.© The Mathematical Association of America. All rights reserved.
PUTNAM EXAM CHALLENGE
1053714_1310.qxp 10/27/08 12:10 PM Page 977
P!x, y" ! 100x0.6y0.4P!x, y" ! 100x0.25y0.75
P!x, y" ! 100x0.4y0.6P!x, y" ! 100x0.25y0.75
x " y ! a.
v2v1
#2#1
sin #1
v1!
sin #2
v2
x $ z ! 0.
n#x1 x2 x3 . . . xn ≤x1 " x2 " x3 " . . . " xn
n.
xi ≥ 0.. . . ! xn, $n
i!1xi ! S,
x1 ! x2 ! x3 !x1 x2 x3 . . . xn
3#xyz ≤x " y " z
3 .
In Exercises 33–42, use Lagrange multipliers to solve the indi-cated exercise in Section 13.9.
33. Exercise 1 34. Exercise 235. Exercise 5 36. Exercise 637. Exercise 9 38. Exercise 1039. Exercise 11 40. Exercise 1241. Exercise 17 42. Exercise 18
43. Maximum Volume Use Lagrange multipliers to find thedimensions of a rectangular box of maximum volume that canbe inscribed (with edges parallel to the coordinate axes) in theellipsoid
45. Minimum Cost A cargo container (in the shape of a rectangularsolid) must have a volume of 480 cubic feet. The bottom willcost $5 per square foot to construct and the sides and the topwill cost $3 per square foot to construct. Use Lagrangemultipliers to find the dimensions of the container of this sizethat has minimum cost.
46. Geometric and Arithmetic Means(a) Use Lagrange multipliers to prove that the product of three
positive numbers and whose sum has the constantvalue is a maximum when the three numbers are equal.Use this result to prove that
(b) Generalize the result of part (a) to prove that the productis a maximum when
and all Then prove that
This shows that the geometric mean is never greater thanthe arithmetic mean.
47. Minimum Surface Area Use Lagrange multipliers to find thedimensions of a right circular cylinder with volume cubicunits and minimum surface area.
48. Temperature Distribution Letrepresent the temperature at each point on the sphere
Find the maximum temperature on thecurve formed by the intersection of the sphere and the plane
49. Refraction of Light When light waves traveling in atransparent medium strike the surface of a second transparentmedium, they tend to “bend” in order to follow the path ofminimum time. This tendency is called refraction and isdescribed by Snell’s Law of Refraction,
where and are the magnitudes of the angles shown in thefigure, and and are the velocities of light in the two media.Use Lagrange multipliers to derive this law using
Figure for 49 Figure for 50
50. Area and Perimeter A semicircle is on top of a rectangle (seefigure). If the area is fixed and the perimeter is a minimum, orif the perimeter is fixed and the area is a maximum, useLagrange multipliers to verify that the length of the rectangle istwice its height.
Production Level In Exercises 51 and 52, find the maximumproduction level if the total cost of labor (at $72 per unit) andcapital (at $60 per unit) is limited to $250,000, where is thenumber of units of labor and is the number of units of capital.
51. 52.
Cost In Exercises 53 and 54, find the minimum cost ofproducing 50,000 units of a product, where is the numberof units of labor (at $72 per unit) and is the number of units ofcapital (at $60 per unit).
53. 54.
55. Investigation Consider the objective function subject to the constraint that , and are
the angles of a triangle.(a) Use Lagrange multipliers to maximize (b) Use the constraint to reduce the function to a function of
two independent variables. Use a computer algebra systemto graph the surface represented by Identify themaximum values on the graph.
g.
gg.
,cos cos cosg , ,
P x, y 100x0.6y0.4P x, y 100x0.25y0.75
yx
P x, y 100x0.4y0.6P x, y 100x0.25y0.75
yx
P
l
h
a
x
d1
y1θ
2θQ
d2
Medium 1
Medium 2
Px y a.
v2v1
21
sin 1
v1
sin 2
v2
x z 0.
x2 y2 z2 50.
T x, y, z 100 x2 y2
V0
n x1x2x3. . . xn
x1 x2 x3. . . xn
n .
xi 0.. . . xn,n
i 1xi S,
x1 x2 x3x1x2x3. . . xn
3 xyz x y z 3.S,
z,y,x,
x2 a2 y2 b2 z2 c2 1.
13.10 Lagrange Multipliers 977
44. The sum of the length and the girth (perimeter of a crosssection) of a package carried by a delivery service cannotexceed 108 inches.(a) Determine whether Lagrange multipliers can be used to
find the dimensions of the rectangular package oflargest volume that may be sent. Explain your reasoning.
(b) If Lagrange multipliers can be used, find the dimen-sions. Compare your answer with that obtained inExercise 38, Section 13.9.
CAPSTONE
CAS
56. A can buoy is to be made of three pieces, namely, a cylinderand two equal cones, the altitude of each cone being equalto the altitude of the cylinder. For a given area of surface, what shape will have the greatest volume?
This problem was composed by the Committee on the Putnam Prize Competition.© The Mathematical Association of America. All rights reserved.
PUTNAM EXAM CHALLENGE
1053714_1310.qxp 10/27/08 12:10 PM Page 977
Preparación del examen Putman56. Una boya está hecha de tres piezas, a saber, un cilindro y dos
conos iguales, la altura de cada uno de los conos es igual ala altura del cilindro. Para una superficie dada, ¿con quéforma se tendrá el volumen máximo?
Este problema fue preparado por el Committee on the Putnam Prize Competition. © The Mathematical Association of America. Todos los derechos reservados.
Para discusión44. La suma de las longitudes y el tamaño (perímetro de una sec-
ción transversal) de un paquete llevado por un servicio deentrega a domicilio no puede exceder 108 pulgadas. a) Determinar si los multiplicadores de Lagrange se pueden
usar para encontrar las dimensiones del paquete rectangu-lar de más grande volumen que puede ser enviado.Explicar el razonamiento.
b) Si se pueden usar los multiplicadores de Lagrange, encon-trar las dimensiones. Comparar su respuesta con la obteni-da en el ejercicio 38, sección 13.9.
sen sen
In Exercises 33–42, use Lagrange multipliers to solve the indi-cated exercise in Section 13.9.
33. Exercise 1 34. Exercise 235. Exercise 5 36. Exercise 637. Exercise 9 38. Exercise 1039. Exercise 11 40. Exercise 1241. Exercise 17 42. Exercise 18
43. Maximum Volume Use Lagrange multipliers to find thedimensions of a rectangular box of maximum volume that canbe inscribed (with edges parallel to the coordinate axes) in theellipsoid
45. Minimum Cost A cargo container (in the shape of a rectangularsolid) must have a volume of 480 cubic feet. The bottom willcost $5 per square foot to construct and the sides and the topwill cost $3 per square foot to construct. Use Lagrangemultipliers to find the dimensions of the container of this sizethat has minimum cost.
46. Geometric and Arithmetic Means(a) Use Lagrange multipliers to prove that the product of three
positive numbers and whose sum has the constantvalue is a maximum when the three numbers are equal.Use this result to prove that
(b) Generalize the result of part (a) to prove that the productis a maximum when
and all Then prove that
This shows that the geometric mean is never greater thanthe arithmetic mean.
47. Minimum Surface Area Use Lagrange multipliers to find thedimensions of a right circular cylinder with volume cubicunits and minimum surface area.
48. Temperature Distribution Letrepresent the temperature at each point on the sphere
Find the maximum temperature on thecurve formed by the intersection of the sphere and the plane
49. Refraction of Light When light waves traveling in atransparent medium strike the surface of a second transparentmedium, they tend to “bend” in order to follow the path ofminimum time. This tendency is called refraction and isdescribed by Snell’s Law of Refraction,
where and are the magnitudes of the angles shown in thefigure, and and are the velocities of light in the two media.Use Lagrange multipliers to derive this law using
Figure for 49 Figure for 50
50. Area and Perimeter A semicircle is on top of a rectangle (seefigure). If the area is fixed and the perimeter is a minimum, orif the perimeter is fixed and the area is a maximum, useLagrange multipliers to verify that the length of the rectangle istwice its height.
Production Level In Exercises 51 and 52, find the maximumproduction level if the total cost of labor (at $72 per unit) andcapital (at $60 per unit) is limited to $250,000, where is thenumber of units of labor and is the number of units of capital.
51. 52.
Cost In Exercises 53 and 54, find the minimum cost ofproducing 50,000 units of a product, where is the numberof units of labor (at $72 per unit) and is the number of units ofcapital (at $60 per unit).
53. 54.
55. Investigation Consider the objective function subject to the constraint that , and are
the angles of a triangle.(a) Use Lagrange multipliers to maximize (b) Use the constraint to reduce the function to a function of
two independent variables. Use a computer algebra systemto graph the surface represented by Identify themaximum values on the graph.
g.
gg.
,cos cos cosg , ,
P x, y 100x0.6y0.4P x, y 100x0.25y0.75
yx
P x, y 100x0.4y0.6P x, y 100x0.25y0.75
yx
P
l
h
a
x
d1
y1θ
2θQ
d2
Medium 1
Medium 2
Px y a.
v2v1
21
sin 1
v1
sin 2
v2
x z 0.
x2 y2 z2 50.
T x, y, z 100 x2 y2
V0
n x1x2x3. . . xn
x1 x2 x3. . . xn
n .
xi 0.. . . xn,n
i 1xi S,
x1 x2 x3x1x2x3. . . xn
3 xyz x y z 3.S,
z,y,x,
x2 a2 y2 b2 z2 c2 1.
13.10 Lagrange Multipliers 977
44. The sum of the length and the girth (perimeter of a crosssection) of a package carried by a delivery service cannotexceed 108 inches.(a) Determine whether Lagrange multipliers can be used to
find the dimensions of the rectangular package oflargest volume that may be sent. Explain your reasoning.
(b) If Lagrange multipliers can be used, find the dimen-sions. Compare your answer with that obtained inExercise 38, Section 13.9.
CAPSTONE
CAS
56. A can buoy is to be made of three pieces, namely, a cylinderand two equal cones, the altitude of each cone being equalto the altitude of the cylinder. For a given area of surface, what shape will have the greatest volume?
This problem was composed by the Committee on the Putnam Prize Competition.© The Mathematical Association of America. All rights reserved.
PUTNAM EXAM CHALLENGE
1053714_1310.qxp 10/27/08 12:10 PM Page 977
a
x
d1
y
2θ
1θ
Q
d2
Medio 1
Medio 2
P
l
h
In Exercises 33–42, use Lagrange multipliers to solve the indi-cated exercise in Section 13.9.
33. Exercise 1 34. Exercise 235. Exercise 5 36. Exercise 637. Exercise 9 38. Exercise 1039. Exercise 11 40. Exercise 1241. Exercise 17 42. Exercise 18
43. Maximum Volume Use Lagrange multipliers to find thedimensions of a rectangular box of maximum volume that canbe inscribed (with edges parallel to the coordinate axes) in theellipsoid
45. Minimum Cost A cargo container (in the shape of a rectangularsolid) must have a volume of 480 cubic feet. The bottom willcost $5 per square foot to construct and the sides and the topwill cost $3 per square foot to construct. Use Lagrangemultipliers to find the dimensions of the container of this sizethat has minimum cost.
46. Geometric and Arithmetic Means(a) Use Lagrange multipliers to prove that the product of three
positive numbers and whose sum has the constantvalue is a maximum when the three numbers are equal.Use this result to prove that
(b) Generalize the result of part (a) to prove that the productis a maximum when
and all Then prove that
This shows that the geometric mean is never greater thanthe arithmetic mean.
47. Minimum Surface Area Use Lagrange multipliers to find thedimensions of a right circular cylinder with volume cubicunits and minimum surface area.
48. Temperature Distribution Letrepresent the temperature at each point on the sphere
Find the maximum temperature on thecurve formed by the intersection of the sphere and the plane
49. Refraction of Light When light waves traveling in atransparent medium strike the surface of a second transparentmedium, they tend to “bend” in order to follow the path ofminimum time. This tendency is called refraction and isdescribed by Snell’s Law of Refraction,
where and are the magnitudes of the angles shown in thefigure, and and are the velocities of light in the two media.Use Lagrange multipliers to derive this law using
Figure for 49 Figure for 50
50. Area and Perimeter A semicircle is on top of a rectangle (seefigure). If the area is fixed and the perimeter is a minimum, orif the perimeter is fixed and the area is a maximum, useLagrange multipliers to verify that the length of the rectangle istwice its height.
Production Level In Exercises 51 and 52, find the maximumproduction level if the total cost of labor (at $72 per unit) andcapital (at $60 per unit) is limited to $250,000, where is thenumber of units of labor and is the number of units of capital.
51. 52.
Cost In Exercises 53 and 54, find the minimum cost ofproducing 50,000 units of a product, where is the numberof units of labor (at $72 per unit) and is the number of units ofcapital (at $60 per unit).
53. 54.
55. Investigation Consider the objective function subject to the constraint that , and are
the angles of a triangle.(a) Use Lagrange multipliers to maximize (b) Use the constraint to reduce the function to a function of
two independent variables. Use a computer algebra systemto graph the surface represented by Identify themaximum values on the graph.
g.
gg.
,cos cos cosg , ,
P x, y 100x0.6y0.4P x, y 100x0.25y0.75
yx
P x, y 100x0.4y0.6P x, y 100x0.25y0.75
yx
P
l
h
a
x
d1
y1θ
2θQ
d2
Medium 1
Medium 2
Px y a.
v2v1
21
sin 1
v1
sin 2
v2
x z 0.
x2 y2 z2 50.
T x, y, z 100 x2 y2
V0
n x1x2x3. . . xn
x1 x2 x3. . . xn
n .
xi 0.. . . xn,n
i 1xi S,
x1 x2 x3x1x2x3. . . xn
3 xyz x y z 3.S,
z,y,x,
x2 a2 y2 b2 z2 c2 1.
13.10 Lagrange Multipliers 977
44. The sum of the length and the girth (perimeter of a crosssection) of a package carried by a delivery service cannotexceed 108 inches.(a) Determine whether Lagrange multipliers can be used to
find the dimensions of the rectangular package oflargest volume that may be sent. Explain your reasoning.
(b) If Lagrange multipliers can be used, find the dimen-sions. Compare your answer with that obtained inExercise 38, Section 13.9.
CAPSTONE
CAS
56. A can buoy is to be made of three pieces, namely, a cylinderand two equal cones, the altitude of each cone being equalto the altitude of the cylinder. For a given area of surface, what shape will have the greatest volume?
This problem was composed by the Committee on the Putnam Prize Competition.© The Mathematical Association of America. All rights reserved.
PUTNAM EXAM CHALLENGE
1053714_1310.qxp 10/27/08 12:10 PM Page 977
Larson-13-10.qxd 3/12/09 19:23 Page 977
SECCIÓN 13.10 Multiplicadores de Lagrange 977
En los ejercicios 33 a 42, usar los multiplicadores de Lagrangepara resolver el ejercicio indicado en la sección 13.9.33. Ejercicio 1 34. Ejercicio 235. Ejercicio 5 36. Ejercicio 637. Ejercicio 9 38. Ejercicio 1039. Ejercicio 11 40. Ejercicio 1241. Ejercicio 17 42. Ejercicio 18
43. Volumen máximo Utilizar multiplicadores de Lagrange para de-terminar las dimensiones de la caja rectangular de volumen máxi-mo que puede ser inscrita (con los bordes paralelos a los ejes decoordenadas) en el elipsoide
45. Costo mínimo Un contenedor de carga (en forma de un sólidorectangular) debe tener un volumen de 480 pies cúbicos. Laparte inferior costará $5 por pie cuadrado para construir, y loslados y la parte superior costarán $3 por pie cuadrado para cons-trucción. Usar los multiplicadores de Lagrange para encontrarlas dimensiones del contenedor de este tamaño que tiene costomínimo.
46. Medias geométrica y aritméticaa) Utilizar los multiplicadores de Lagrange para demostrar que
el producto de tres números positivos x, y y z cuya suma tieneun valor constante S, es máximo cuando los tres números soniguales. Utilizar este resultado para demostrar que
b) Generalizar el resultado del inciso a) para demostrar que elproducto es máximo cuando
y todo Después, demostrar que
Esto demuestra que la media geométrica nunca es mayorque la media aritmética.
47. Superficie mínima Utilizar multiplicadores de Lagrange paraencontrar las dimensiones de un cilindro circular recto con vo-lumen de V0 unidades cúbicas y superficie mínima.
48. Distribución de temperatura Sea la temperatura en cada punto sobre la esfera x2 ! y2 ! z2
" 50. Hallar la temperatura máxima en la curva formada por laintersección de la esfera y el plano
49. Refracción de la luz Cuando las ondas de luz que viajan en unmedio transparente atraviesan la superficie de un segundo mediotransparente, tienden a “desviarse” para seguir la trayectoria detiempo mínimo. Esta tendencia se llama refracción y está descri-ta por la ley de refracción de Snell, según la cual
donde y son las magnitudes de los ángulos mostrados en lafigura, y y son las velocidades de la luz en los dos medios.Utilizar los multiplicadores de Lagrange para deducir esta leyusando
Figura para 49 Figura para 50
50. Área y perímetro Un semicírculo está sobre un rectángulo (verla figura). Si el área es fija y el perímetro es un mínimo, o si elperímetro es fijo y el área es un máximo, utilizar multiplicadoresde Lagrange para verificar que la longitud del rectángulo es eldoble de su altura.
Nivel de producción En los ejercicios 51 y 52, hallar el máximonivel de producción P si el costo total de trabajo (a $72 porunidad) y capital (a $60 por unidad) está restringido a $250 000,donde x es el número de unidades de trabajo y y es el número deunidades de capital.
51. 52.
Costo En los ejercicios 53 y 54, hallar el costo mínimo para pro-ducir 50 000 unidades de un producto donde x es el número deunidades de trabajo (a $72 por unidad) y y es el número de uni-dades de capital (a $60 por unidad).
53. 54.
55. Investigación Considerar la función objetivo sujeta a la restricción o ligadura de que #, $
y % sean los ángulos de un triángulo.a) Utilizar los multiplicadores de Lagrange para maximizar b) Utilizar la restricción o ligadura para reducir la función g a
una función de dos variables independientes. Utilizar un sis-tema algebraico por computadora para representar gráfica-mente la superficie definida por g. Identificar en la gráfica losvalores máximos.
g.
In Exercises 33–42, use Lagrange multipliers to solve the indi-cated exercise in Section 13.9.
33. Exercise 1 34. Exercise 235. Exercise 5 36. Exercise 637. Exercise 9 38. Exercise 1039. Exercise 11 40. Exercise 1241. Exercise 17 42. Exercise 18
43. Maximum Volume Use Lagrange multipliers to find thedimensions of a rectangular box of maximum volume that canbe inscribed (with edges parallel to the coordinate axes) in theellipsoid
45. Minimum Cost A cargo container (in the shape of a rectangularsolid) must have a volume of 480 cubic feet. The bottom willcost $5 per square foot to construct and the sides and the topwill cost $3 per square foot to construct. Use Lagrangemultipliers to find the dimensions of the container of this sizethat has minimum cost.
46. Geometric and Arithmetic Means(a) Use Lagrange multipliers to prove that the product of three
positive numbers and whose sum has the constantvalue is a maximum when the three numbers are equal.Use this result to prove that
(b) Generalize the result of part (a) to prove that the productis a maximum when
and all Then prove that
This shows that the geometric mean is never greater thanthe arithmetic mean.
47. Minimum Surface Area Use Lagrange multipliers to find thedimensions of a right circular cylinder with volume cubicunits and minimum surface area.
48. Temperature Distribution Letrepresent the temperature at each point on the sphere
Find the maximum temperature on thecurve formed by the intersection of the sphere and the plane
49. Refraction of Light When light waves traveling in atransparent medium strike the surface of a second transparentmedium, they tend to “bend” in order to follow the path ofminimum time. This tendency is called refraction and isdescribed by Snell’s Law of Refraction,
where and are the magnitudes of the angles shown in thefigure, and and are the velocities of light in the two media.Use Lagrange multipliers to derive this law using
Figure for 49 Figure for 50
50. Area and Perimeter A semicircle is on top of a rectangle (seefigure). If the area is fixed and the perimeter is a minimum, orif the perimeter is fixed and the area is a maximum, useLagrange multipliers to verify that the length of the rectangle istwice its height.
Production Level In Exercises 51 and 52, find the maximumproduction level if the total cost of labor (at $72 per unit) andcapital (at $60 per unit) is limited to $250,000, where is thenumber of units of labor and is the number of units of capital.
51. 52.
Cost In Exercises 53 and 54, find the minimum cost ofproducing 50,000 units of a product, where is the numberof units of labor (at $72 per unit) and is the number of units ofcapital (at $60 per unit).
53. 54.
55. Investigation Consider the objective function subject to the constraint that , and are
the angles of a triangle.(a) Use Lagrange multipliers to maximize (b) Use the constraint to reduce the function to a function of
two independent variables. Use a computer algebra systemto graph the surface represented by Identify themaximum values on the graph.
g.
gg.
,cos cos cosg , ,
P x, y 100x0.6y0.4P x, y 100x0.25y0.75
yx
P x, y 100x0.4y0.6P x, y 100x0.25y0.75
yx
P
l
h
a
x
d1
y1θ
2θQ
d2
Medium 1
Medium 2
Px y a.
v2v1
21
sin 1
v1
sin 2
v2
x z 0.
x2 y2 z2 50.
T x, y, z 100 x2 y2
V0
n x1x2x3. . . xn
x1 x2 x3. . . xn
n .
xi 0.. . . xn,n
i 1xi S,
x1 x2 x3x1x2x3. . . xn
3 xyz x y z 3.S,
z,y,x,
x2 a2 y2 b2 z2 c2 1.
13.10 Lagrange Multipliers 977
44. The sum of the length and the girth (perimeter of a crosssection) of a package carried by a delivery service cannotexceed 108 inches.(a) Determine whether Lagrange multipliers can be used to
find the dimensions of the rectangular package oflargest volume that may be sent. Explain your reasoning.
(b) If Lagrange multipliers can be used, find the dimen-sions. Compare your answer with that obtained inExercise 38, Section 13.9.
CAPSTONE
CAS
56. A can buoy is to be made of three pieces, namely, a cylinderand two equal cones, the altitude of each cone being equalto the altitude of the cylinder. For a given area of surface, what shape will have the greatest volume?
This problem was composed by the Committee on the Putnam Prize Competition.© The Mathematical Association of America. All rights reserved.
PUTNAM EXAM CHALLENGE
1053714_1310.qxp 10/27/08 12:10 PM Page 977
In Exercises 33–42, use Lagrange multipliers to solve the indi-cated exercise in Section 13.9.
33. Exercise 1 34. Exercise 235. Exercise 5 36. Exercise 637. Exercise 9 38. Exercise 1039. Exercise 11 40. Exercise 1241. Exercise 17 42. Exercise 18
43. Maximum Volume Use Lagrange multipliers to find thedimensions of a rectangular box of maximum volume that canbe inscribed (with edges parallel to the coordinate axes) in theellipsoid
45. Minimum Cost A cargo container (in the shape of a rectangularsolid) must have a volume of 480 cubic feet. The bottom willcost $5 per square foot to construct and the sides and the topwill cost $3 per square foot to construct. Use Lagrangemultipliers to find the dimensions of the container of this sizethat has minimum cost.
46. Geometric and Arithmetic Means(a) Use Lagrange multipliers to prove that the product of three
positive numbers and whose sum has the constantvalue is a maximum when the three numbers are equal.Use this result to prove that
(b) Generalize the result of part (a) to prove that the productis a maximum when
and all Then prove that
This shows that the geometric mean is never greater thanthe arithmetic mean.
47. Minimum Surface Area Use Lagrange multipliers to find thedimensions of a right circular cylinder with volume cubicunits and minimum surface area.
48. Temperature Distribution Letrepresent the temperature at each point on the sphere
Find the maximum temperature on thecurve formed by the intersection of the sphere and the plane
49. Refraction of Light When light waves traveling in atransparent medium strike the surface of a second transparentmedium, they tend to “bend” in order to follow the path ofminimum time. This tendency is called refraction and isdescribed by Snell’s Law of Refraction,
where and are the magnitudes of the angles shown in thefigure, and and are the velocities of light in the two media.Use Lagrange multipliers to derive this law using
Figure for 49 Figure for 50
50. Area and Perimeter A semicircle is on top of a rectangle (seefigure). If the area is fixed and the perimeter is a minimum, orif the perimeter is fixed and the area is a maximum, useLagrange multipliers to verify that the length of the rectangle istwice its height.
Production Level In Exercises 51 and 52, find the maximumproduction level if the total cost of labor (at $72 per unit) andcapital (at $60 per unit) is limited to $250,000, where is thenumber of units of labor and is the number of units of capital.
51. 52.
Cost In Exercises 53 and 54, find the minimum cost ofproducing 50,000 units of a product, where is the numberof units of labor (at $72 per unit) and is the number of units ofcapital (at $60 per unit).
53. 54.
55. Investigation Consider the objective function subject to the constraint that , and are
the angles of a triangle.(a) Use Lagrange multipliers to maximize (b) Use the constraint to reduce the function to a function of
two independent variables. Use a computer algebra systemto graph the surface represented by Identify themaximum values on the graph.
g.
gg.
,cos cos cosg , ,
P x, y 100x0.6y0.4P x, y 100x0.25y0.75
yx
P x, y 100x0.4y0.6P x, y 100x0.25y0.75
yx
P
l
h
a
x
d1
y1θ
2θQ
d2
Medium 1
Medium 2
Px y a.
v2v1
21
sin 1
v1
sin 2
v2
x z 0.
x2 y2 z2 50.
T x, y, z 100 x2 y2
V0
n x1x2x3. . . xn
x1 x2 x3. . . xn
n .
xi 0.. . . xn,n
i 1xi S,
x1 x2 x3x1x2x3. . . xn
3 xyz x y z 3.S,
z,y,x,
x2 a2 y2 b2 z2 c2 1.
13.10 Lagrange Multipliers 977
44. The sum of the length and the girth (perimeter of a crosssection) of a package carried by a delivery service cannotexceed 108 inches.(a) Determine whether Lagrange multipliers can be used to
find the dimensions of the rectangular package oflargest volume that may be sent. Explain your reasoning.
(b) If Lagrange multipliers can be used, find the dimen-sions. Compare your answer with that obtained inExercise 38, Section 13.9.
CAPSTONE
CAS
56. A can buoy is to be made of three pieces, namely, a cylinderand two equal cones, the altitude of each cone being equalto the altitude of the cylinder. For a given area of surface, what shape will have the greatest volume?
This problem was composed by the Committee on the Putnam Prize Competition.© The Mathematical Association of America. All rights reserved.
PUTNAM EXAM CHALLENGE
1053714_1310.qxp 10/27/08 12:10 PM Page 977
P!x, y" ! 100x0.6y0.4P!x, y" ! 100x0.25y0.75
P!x, y" ! 100x0.4y0.6P!x, y" ! 100x0.25y0.75
x " y ! a.
v2v1
#2#1
sin #1
v1!
sin #2
v2
x $ z ! 0.
n#x1 x2 x3 . . . xn ≤x1 " x2 " x3 " . . . " xn
n.
xi ≥ 0.. . . ! xn, $n
i!1xi ! S,
x1 ! x2 ! x3 !x1 x2 x3 . . . xn
3#xyz ≤x " y " z
3 .
In Exercises 33–42, use Lagrange multipliers to solve the indi-cated exercise in Section 13.9.
33. Exercise 1 34. Exercise 235. Exercise 5 36. Exercise 637. Exercise 9 38. Exercise 1039. Exercise 11 40. Exercise 1241. Exercise 17 42. Exercise 18
43. Maximum Volume Use Lagrange multipliers to find thedimensions of a rectangular box of maximum volume that canbe inscribed (with edges parallel to the coordinate axes) in theellipsoid
45. Minimum Cost A cargo container (in the shape of a rectangularsolid) must have a volume of 480 cubic feet. The bottom willcost $5 per square foot to construct and the sides and the topwill cost $3 per square foot to construct. Use Lagrangemultipliers to find the dimensions of the container of this sizethat has minimum cost.
46. Geometric and Arithmetic Means(a) Use Lagrange multipliers to prove that the product of three
positive numbers and whose sum has the constantvalue is a maximum when the three numbers are equal.Use this result to prove that
(b) Generalize the result of part (a) to prove that the productis a maximum when
and all Then prove that
This shows that the geometric mean is never greater thanthe arithmetic mean.
47. Minimum Surface Area Use Lagrange multipliers to find thedimensions of a right circular cylinder with volume cubicunits and minimum surface area.
48. Temperature Distribution Letrepresent the temperature at each point on the sphere
Find the maximum temperature on thecurve formed by the intersection of the sphere and the plane
49. Refraction of Light When light waves traveling in atransparent medium strike the surface of a second transparentmedium, they tend to “bend” in order to follow the path ofminimum time. This tendency is called refraction and isdescribed by Snell’s Law of Refraction,
where and are the magnitudes of the angles shown in thefigure, and and are the velocities of light in the two media.Use Lagrange multipliers to derive this law using
Figure for 49 Figure for 50
50. Area and Perimeter A semicircle is on top of a rectangle (seefigure). If the area is fixed and the perimeter is a minimum, orif the perimeter is fixed and the area is a maximum, useLagrange multipliers to verify that the length of the rectangle istwice its height.
Production Level In Exercises 51 and 52, find the maximumproduction level if the total cost of labor (at $72 per unit) andcapital (at $60 per unit) is limited to $250,000, where is thenumber of units of labor and is the number of units of capital.
51. 52.
Cost In Exercises 53 and 54, find the minimum cost ofproducing 50,000 units of a product, where is the numberof units of labor (at $72 per unit) and is the number of units ofcapital (at $60 per unit).
53. 54.
55. Investigation Consider the objective function subject to the constraint that , and are
the angles of a triangle.(a) Use Lagrange multipliers to maximize (b) Use the constraint to reduce the function to a function of
two independent variables. Use a computer algebra systemto graph the surface represented by Identify themaximum values on the graph.
g.
gg.
,cos cos cosg , ,
P x, y 100x0.6y0.4P x, y 100x0.25y0.75
yx
P x, y 100x0.4y0.6P x, y 100x0.25y0.75
yx
P
l
h
a
x
d1
y1θ
2θQ
d2
Medium 1
Medium 2
Px y a.
v2v1
21
sin 1
v1
sin 2
v2
x z 0.
x2 y2 z2 50.
T x, y, z 100 x2 y2
V0
n x1x2x3. . . xn
x1 x2 x3. . . xn
n .
xi 0.. . . xn,n
i 1xi S,
x1 x2 x3x1x2x3. . . xn
3 xyz x y z 3.S,
z,y,x,
x2 a2 y2 b2 z2 c2 1.
13.10 Lagrange Multipliers 977
44. The sum of the length and the girth (perimeter of a crosssection) of a package carried by a delivery service cannotexceed 108 inches.(a) Determine whether Lagrange multipliers can be used to
find the dimensions of the rectangular package oflargest volume that may be sent. Explain your reasoning.
(b) If Lagrange multipliers can be used, find the dimen-sions. Compare your answer with that obtained inExercise 38, Section 13.9.
CAPSTONE
CAS
56. A can buoy is to be made of three pieces, namely, a cylinderand two equal cones, the altitude of each cone being equalto the altitude of the cylinder. For a given area of surface, what shape will have the greatest volume?
This problem was composed by the Committee on the Putnam Prize Competition.© The Mathematical Association of America. All rights reserved.
PUTNAM EXAM CHALLENGE
1053714_1310.qxp 10/27/08 12:10 PM Page 977
Preparación del examen Putman56. Una boya está hecha de tres piezas, a saber, un cilindro y dos
conos iguales, la altura de cada uno de los conos es igual ala altura del cilindro. Para una superficie dada, ¿con quéforma se tendrá el volumen máximo?
Este problema fue preparado por el Committee on the Putnam Prize Competition. © The Mathematical Association of America. Todos los derechos reservados.
Para discusión44. La suma de las longitudes y el tamaño (perímetro de una sec-
ción transversal) de un paquete llevado por un servicio deentrega a domicilio no puede exceder 108 pulgadas. a) Determinar si los multiplicadores de Lagrange se pueden
usar para encontrar las dimensiones del paquete rectangu-lar de más grande volumen que puede ser enviado.Explicar el razonamiento.
b) Si se pueden usar los multiplicadores de Lagrange, encon-trar las dimensiones. Comparar su respuesta con la obteni-da en el ejercicio 38, sección 13.9.
sen sen
In Exercises 33–42, use Lagrange multipliers to solve the indi-cated exercise in Section 13.9.
33. Exercise 1 34. Exercise 235. Exercise 5 36. Exercise 637. Exercise 9 38. Exercise 1039. Exercise 11 40. Exercise 1241. Exercise 17 42. Exercise 18
43. Maximum Volume Use Lagrange multipliers to find thedimensions of a rectangular box of maximum volume that canbe inscribed (with edges parallel to the coordinate axes) in theellipsoid
45. Minimum Cost A cargo container (in the shape of a rectangularsolid) must have a volume of 480 cubic feet. The bottom willcost $5 per square foot to construct and the sides and the topwill cost $3 per square foot to construct. Use Lagrangemultipliers to find the dimensions of the container of this sizethat has minimum cost.
46. Geometric and Arithmetic Means(a) Use Lagrange multipliers to prove that the product of three
positive numbers and whose sum has the constantvalue is a maximum when the three numbers are equal.Use this result to prove that
(b) Generalize the result of part (a) to prove that the productis a maximum when
and all Then prove that
This shows that the geometric mean is never greater thanthe arithmetic mean.
47. Minimum Surface Area Use Lagrange multipliers to find thedimensions of a right circular cylinder with volume cubicunits and minimum surface area.
48. Temperature Distribution Letrepresent the temperature at each point on the sphere
Find the maximum temperature on thecurve formed by the intersection of the sphere and the plane
49. Refraction of Light When light waves traveling in atransparent medium strike the surface of a second transparentmedium, they tend to “bend” in order to follow the path ofminimum time. This tendency is called refraction and isdescribed by Snell’s Law of Refraction,
where and are the magnitudes of the angles shown in thefigure, and and are the velocities of light in the two media.Use Lagrange multipliers to derive this law using
Figure for 49 Figure for 50
50. Area and Perimeter A semicircle is on top of a rectangle (seefigure). If the area is fixed and the perimeter is a minimum, orif the perimeter is fixed and the area is a maximum, useLagrange multipliers to verify that the length of the rectangle istwice its height.
Production Level In Exercises 51 and 52, find the maximumproduction level if the total cost of labor (at $72 per unit) andcapital (at $60 per unit) is limited to $250,000, where is thenumber of units of labor and is the number of units of capital.
51. 52.
Cost In Exercises 53 and 54, find the minimum cost ofproducing 50,000 units of a product, where is the numberof units of labor (at $72 per unit) and is the number of units ofcapital (at $60 per unit).
53. 54.
55. Investigation Consider the objective function subject to the constraint that , and are
the angles of a triangle.(a) Use Lagrange multipliers to maximize (b) Use the constraint to reduce the function to a function of
two independent variables. Use a computer algebra systemto graph the surface represented by Identify themaximum values on the graph.
g.
gg.
,cos cos cosg , ,
P x, y 100x0.6y0.4P x, y 100x0.25y0.75
yx
P x, y 100x0.4y0.6P x, y 100x0.25y0.75
yx
P
l
h
a
x
d1
y1θ
2θQ
d2
Medium 1
Medium 2
Px y a.
v2v1
21
sin 1
v1
sin 2
v2
x z 0.
x2 y2 z2 50.
T x, y, z 100 x2 y2
V0
n x1x2x3. . . xn
x1 x2 x3. . . xn
n .
xi 0.. . . xn,n
i 1xi S,
x1 x2 x3x1x2x3. . . xn
3 xyz x y z 3.S,
z,y,x,
x2 a2 y2 b2 z2 c2 1.
13.10 Lagrange Multipliers 977
44. The sum of the length and the girth (perimeter of a crosssection) of a package carried by a delivery service cannotexceed 108 inches.(a) Determine whether Lagrange multipliers can be used to
find the dimensions of the rectangular package oflargest volume that may be sent. Explain your reasoning.
(b) If Lagrange multipliers can be used, find the dimen-sions. Compare your answer with that obtained inExercise 38, Section 13.9.
CAPSTONE
CAS
56. A can buoy is to be made of three pieces, namely, a cylinderand two equal cones, the altitude of each cone being equalto the altitude of the cylinder. For a given area of surface, what shape will have the greatest volume?
This problem was composed by the Committee on the Putnam Prize Competition.© The Mathematical Association of America. All rights reserved.
PUTNAM EXAM CHALLENGE
1053714_1310.qxp 10/27/08 12:10 PM Page 977
a
x
d1
y
2θ
1θ
Q
d2
Medio 1
Medio 2
P
l
h
In Exercises 33–42, use Lagrange multipliers to solve the indi-cated exercise in Section 13.9.
33. Exercise 1 34. Exercise 235. Exercise 5 36. Exercise 637. Exercise 9 38. Exercise 1039. Exercise 11 40. Exercise 1241. Exercise 17 42. Exercise 18
43. Maximum Volume Use Lagrange multipliers to find thedimensions of a rectangular box of maximum volume that canbe inscribed (with edges parallel to the coordinate axes) in theellipsoid
45. Minimum Cost A cargo container (in the shape of a rectangularsolid) must have a volume of 480 cubic feet. The bottom willcost $5 per square foot to construct and the sides and the topwill cost $3 per square foot to construct. Use Lagrangemultipliers to find the dimensions of the container of this sizethat has minimum cost.
46. Geometric and Arithmetic Means(a) Use Lagrange multipliers to prove that the product of three
positive numbers and whose sum has the constantvalue is a maximum when the three numbers are equal.Use this result to prove that
(b) Generalize the result of part (a) to prove that the productis a maximum when
and all Then prove that
This shows that the geometric mean is never greater thanthe arithmetic mean.
47. Minimum Surface Area Use Lagrange multipliers to find thedimensions of a right circular cylinder with volume cubicunits and minimum surface area.
48. Temperature Distribution Letrepresent the temperature at each point on the sphere
Find the maximum temperature on thecurve formed by the intersection of the sphere and the plane
49. Refraction of Light When light waves traveling in atransparent medium strike the surface of a second transparentmedium, they tend to “bend” in order to follow the path ofminimum time. This tendency is called refraction and isdescribed by Snell’s Law of Refraction,
where and are the magnitudes of the angles shown in thefigure, and and are the velocities of light in the two media.Use Lagrange multipliers to derive this law using
Figure for 49 Figure for 50
50. Area and Perimeter A semicircle is on top of a rectangle (seefigure). If the area is fixed and the perimeter is a minimum, orif the perimeter is fixed and the area is a maximum, useLagrange multipliers to verify that the length of the rectangle istwice its height.
Production Level In Exercises 51 and 52, find the maximumproduction level if the total cost of labor (at $72 per unit) andcapital (at $60 per unit) is limited to $250,000, where is thenumber of units of labor and is the number of units of capital.
51. 52.
Cost In Exercises 53 and 54, find the minimum cost ofproducing 50,000 units of a product, where is the numberof units of labor (at $72 per unit) and is the number of units ofcapital (at $60 per unit).
53. 54.
55. Investigation Consider the objective function subject to the constraint that , and are
the angles of a triangle.(a) Use Lagrange multipliers to maximize (b) Use the constraint to reduce the function to a function of
two independent variables. Use a computer algebra systemto graph the surface represented by Identify themaximum values on the graph.
g.
gg.
,cos cos cosg , ,
P x, y 100x0.6y0.4P x, y 100x0.25y0.75
yx
P x, y 100x0.4y0.6P x, y 100x0.25y0.75
yx
P
l
h
a
x
d1
y1θ
2θQ
d2
Medium 1
Medium 2
Px y a.
v2v1
21
sin 1
v1
sin 2
v2
x z 0.
x2 y2 z2 50.
T x, y, z 100 x2 y2
V0
n x1x2x3. . . xn
x1 x2 x3. . . xn
n .
xi 0.. . . xn,n
i 1xi S,
x1 x2 x3x1x2x3. . . xn
3 xyz x y z 3.S,
z,y,x,
x2 a2 y2 b2 z2 c2 1.
13.10 Lagrange Multipliers 977
44. The sum of the length and the girth (perimeter of a crosssection) of a package carried by a delivery service cannotexceed 108 inches.(a) Determine whether Lagrange multipliers can be used to
find the dimensions of the rectangular package oflargest volume that may be sent. Explain your reasoning.
(b) If Lagrange multipliers can be used, find the dimen-sions. Compare your answer with that obtained inExercise 38, Section 13.9.
CAPSTONE
CAS
56. A can buoy is to be made of three pieces, namely, a cylinderand two equal cones, the altitude of each cone being equalto the altitude of the cylinder. For a given area of surface, what shape will have the greatest volume?
This problem was composed by the Committee on the Putnam Prize Competition.© The Mathematical Association of America. All rights reserved.
PUTNAM EXAM CHALLENGE
1053714_1310.qxp 10/27/08 12:10 PM Page 977
Larson-13-10.qxd 3/12/09 19:23 Page 977
SECCIÓN 13.10 Multiplicadores de Lagrange 977
En los ejercicios 33 a 42, usar los multiplicadores de Lagrangepara resolver el ejercicio indicado en la sección 13.9.33. Ejercicio 1 34. Ejercicio 235. Ejercicio 5 36. Ejercicio 637. Ejercicio 9 38. Ejercicio 1039. Ejercicio 11 40. Ejercicio 1241. Ejercicio 17 42. Ejercicio 18
43. Volumen máximo Utilizar multiplicadores de Lagrange para de-terminar las dimensiones de la caja rectangular de volumen máxi-mo que puede ser inscrita (con los bordes paralelos a los ejes decoordenadas) en el elipsoide
45. Costo mínimo Un contenedor de carga (en forma de un sólidorectangular) debe tener un volumen de 480 pies cúbicos. Laparte inferior costará $5 por pie cuadrado para construir, y loslados y la parte superior costarán $3 por pie cuadrado para cons-trucción. Usar los multiplicadores de Lagrange para encontrarlas dimensiones del contenedor de este tamaño que tiene costomínimo.
46. Medias geométrica y aritméticaa) Utilizar los multiplicadores de Lagrange para demostrar que
el producto de tres números positivos x, y y z cuya suma tieneun valor constante S, es máximo cuando los tres números soniguales. Utilizar este resultado para demostrar que
b) Generalizar el resultado del inciso a) para demostrar que elproducto es máximo cuando
y todo Después, demostrar que
Esto demuestra que la media geométrica nunca es mayorque la media aritmética.
47. Superficie mínima Utilizar multiplicadores de Lagrange paraencontrar las dimensiones de un cilindro circular recto con vo-lumen de V0 unidades cúbicas y superficie mínima.
48. Distribución de temperatura Sea la temperatura en cada punto sobre la esfera x2 ! y2 ! z2
" 50. Hallar la temperatura máxima en la curva formada por laintersección de la esfera y el plano
49. Refracción de la luz Cuando las ondas de luz que viajan en unmedio transparente atraviesan la superficie de un segundo mediotransparente, tienden a “desviarse” para seguir la trayectoria detiempo mínimo. Esta tendencia se llama refracción y está descri-ta por la ley de refracción de Snell, según la cual
donde y son las magnitudes de los ángulos mostrados en lafigura, y y son las velocidades de la luz en los dos medios.Utilizar los multiplicadores de Lagrange para deducir esta leyusando
Figura para 49 Figura para 50
50. Área y perímetro Un semicírculo está sobre un rectángulo (verla figura). Si el área es fija y el perímetro es un mínimo, o si elperímetro es fijo y el área es un máximo, utilizar multiplicadoresde Lagrange para verificar que la longitud del rectángulo es eldoble de su altura.
Nivel de producción En los ejercicios 51 y 52, hallar el máximonivel de producción P si el costo total de trabajo (a $72 porunidad) y capital (a $60 por unidad) está restringido a $250 000,donde x es el número de unidades de trabajo y y es el número deunidades de capital.
51. 52.
Costo En los ejercicios 53 y 54, hallar el costo mínimo para pro-ducir 50 000 unidades de un producto donde x es el número deunidades de trabajo (a $72 por unidad) y y es el número de uni-dades de capital (a $60 por unidad).
53. 54.
55. Investigación Considerar la función objetivo sujeta a la restricción o ligadura de que #, $
y % sean los ángulos de un triángulo.a) Utilizar los multiplicadores de Lagrange para maximizar b) Utilizar la restricción o ligadura para reducir la función g a
una función de dos variables independientes. Utilizar un sis-tema algebraico por computadora para representar gráfica-mente la superficie definida por g. Identificar en la gráfica losvalores máximos.
g.
In Exercises 33–42, use Lagrange multipliers to solve the indi-cated exercise in Section 13.9.
33. Exercise 1 34. Exercise 235. Exercise 5 36. Exercise 637. Exercise 9 38. Exercise 1039. Exercise 11 40. Exercise 1241. Exercise 17 42. Exercise 18
43. Maximum Volume Use Lagrange multipliers to find thedimensions of a rectangular box of maximum volume that canbe inscribed (with edges parallel to the coordinate axes) in theellipsoid
45. Minimum Cost A cargo container (in the shape of a rectangularsolid) must have a volume of 480 cubic feet. The bottom willcost $5 per square foot to construct and the sides and the topwill cost $3 per square foot to construct. Use Lagrangemultipliers to find the dimensions of the container of this sizethat has minimum cost.
46. Geometric and Arithmetic Means(a) Use Lagrange multipliers to prove that the product of three
positive numbers and whose sum has the constantvalue is a maximum when the three numbers are equal.Use this result to prove that
(b) Generalize the result of part (a) to prove that the productis a maximum when
and all Then prove that
This shows that the geometric mean is never greater thanthe arithmetic mean.
47. Minimum Surface Area Use Lagrange multipliers to find thedimensions of a right circular cylinder with volume cubicunits and minimum surface area.
48. Temperature Distribution Letrepresent the temperature at each point on the sphere
Find the maximum temperature on thecurve formed by the intersection of the sphere and the plane
49. Refraction of Light When light waves traveling in atransparent medium strike the surface of a second transparentmedium, they tend to “bend” in order to follow the path ofminimum time. This tendency is called refraction and isdescribed by Snell’s Law of Refraction,
where and are the magnitudes of the angles shown in thefigure, and and are the velocities of light in the two media.Use Lagrange multipliers to derive this law using
Figure for 49 Figure for 50
50. Area and Perimeter A semicircle is on top of a rectangle (seefigure). If the area is fixed and the perimeter is a minimum, orif the perimeter is fixed and the area is a maximum, useLagrange multipliers to verify that the length of the rectangle istwice its height.
Production Level In Exercises 51 and 52, find the maximumproduction level if the total cost of labor (at $72 per unit) andcapital (at $60 per unit) is limited to $250,000, where is thenumber of units of labor and is the number of units of capital.
51. 52.
Cost In Exercises 53 and 54, find the minimum cost ofproducing 50,000 units of a product, where is the numberof units of labor (at $72 per unit) and is the number of units ofcapital (at $60 per unit).
53. 54.
55. Investigation Consider the objective function subject to the constraint that , and are
the angles of a triangle.(a) Use Lagrange multipliers to maximize (b) Use the constraint to reduce the function to a function of
two independent variables. Use a computer algebra systemto graph the surface represented by Identify themaximum values on the graph.
g.
gg.
,cos cos cosg , ,
P x, y 100x0.6y0.4P x, y 100x0.25y0.75
yx
P x, y 100x0.4y0.6P x, y 100x0.25y0.75
yx
P
l
h
a
x
d1
y1θ
2θQ
d2
Medium 1
Medium 2
Px y a.
v2v1
21
sin 1
v1
sin 2
v2
x z 0.
x2 y2 z2 50.
T x, y, z 100 x2 y2
V0
n x1x2x3. . . xn
x1 x2 x3. . . xn
n .
xi 0.. . . xn,n
i 1xi S,
x1 x2 x3x1x2x3. . . xn
3 xyz x y z 3.S,
z,y,x,
x2 a2 y2 b2 z2 c2 1.
13.10 Lagrange Multipliers 977
44. The sum of the length and the girth (perimeter of a crosssection) of a package carried by a delivery service cannotexceed 108 inches.(a) Determine whether Lagrange multipliers can be used to
find the dimensions of the rectangular package oflargest volume that may be sent. Explain your reasoning.
(b) If Lagrange multipliers can be used, find the dimen-sions. Compare your answer with that obtained inExercise 38, Section 13.9.
CAPSTONE
CAS
56. A can buoy is to be made of three pieces, namely, a cylinderand two equal cones, the altitude of each cone being equalto the altitude of the cylinder. For a given area of surface, what shape will have the greatest volume?
This problem was composed by the Committee on the Putnam Prize Competition.© The Mathematical Association of America. All rights reserved.
PUTNAM EXAM CHALLENGE
1053714_1310.qxp 10/27/08 12:10 PM Page 977
In Exercises 33–42, use Lagrange multipliers to solve the indi-cated exercise in Section 13.9.
33. Exercise 1 34. Exercise 235. Exercise 5 36. Exercise 637. Exercise 9 38. Exercise 1039. Exercise 11 40. Exercise 1241. Exercise 17 42. Exercise 18
43. Maximum Volume Use Lagrange multipliers to find thedimensions of a rectangular box of maximum volume that canbe inscribed (with edges parallel to the coordinate axes) in theellipsoid
45. Minimum Cost A cargo container (in the shape of a rectangularsolid) must have a volume of 480 cubic feet. The bottom willcost $5 per square foot to construct and the sides and the topwill cost $3 per square foot to construct. Use Lagrangemultipliers to find the dimensions of the container of this sizethat has minimum cost.
46. Geometric and Arithmetic Means(a) Use Lagrange multipliers to prove that the product of three
positive numbers and whose sum has the constantvalue is a maximum when the three numbers are equal.Use this result to prove that
(b) Generalize the result of part (a) to prove that the productis a maximum when
and all Then prove that
This shows that the geometric mean is never greater thanthe arithmetic mean.
47. Minimum Surface Area Use Lagrange multipliers to find thedimensions of a right circular cylinder with volume cubicunits and minimum surface area.
48. Temperature Distribution Letrepresent the temperature at each point on the sphere
Find the maximum temperature on thecurve formed by the intersection of the sphere and the plane
49. Refraction of Light When light waves traveling in atransparent medium strike the surface of a second transparentmedium, they tend to “bend” in order to follow the path ofminimum time. This tendency is called refraction and isdescribed by Snell’s Law of Refraction,
where and are the magnitudes of the angles shown in thefigure, and and are the velocities of light in the two media.Use Lagrange multipliers to derive this law using
Figure for 49 Figure for 50
50. Area and Perimeter A semicircle is on top of a rectangle (seefigure). If the area is fixed and the perimeter is a minimum, orif the perimeter is fixed and the area is a maximum, useLagrange multipliers to verify that the length of the rectangle istwice its height.
Production Level In Exercises 51 and 52, find the maximumproduction level if the total cost of labor (at $72 per unit) andcapital (at $60 per unit) is limited to $250,000, where is thenumber of units of labor and is the number of units of capital.
51. 52.
Cost In Exercises 53 and 54, find the minimum cost ofproducing 50,000 units of a product, where is the numberof units of labor (at $72 per unit) and is the number of units ofcapital (at $60 per unit).
53. 54.
55. Investigation Consider the objective function subject to the constraint that , and are
the angles of a triangle.(a) Use Lagrange multipliers to maximize (b) Use the constraint to reduce the function to a function of
two independent variables. Use a computer algebra systemto graph the surface represented by Identify themaximum values on the graph.
g.
gg.
,cos cos cosg , ,
P x, y 100x0.6y0.4P x, y 100x0.25y0.75
yx
P x, y 100x0.4y0.6P x, y 100x0.25y0.75
yx
P
l
h
a
x
d1
y1θ
2θQ
d2
Medium 1
Medium 2
Px y a.
v2v1
21
sin 1
v1
sin 2
v2
x z 0.
x2 y2 z2 50.
T x, y, z 100 x2 y2
V0
n x1x2x3. . . xn
x1 x2 x3. . . xn
n .
xi 0.. . . xn,n
i 1xi S,
x1 x2 x3x1x2x3. . . xn
3 xyz x y z 3.S,
z,y,x,
x2 a2 y2 b2 z2 c2 1.
13.10 Lagrange Multipliers 977
44. The sum of the length and the girth (perimeter of a crosssection) of a package carried by a delivery service cannotexceed 108 inches.(a) Determine whether Lagrange multipliers can be used to
find the dimensions of the rectangular package oflargest volume that may be sent. Explain your reasoning.
(b) If Lagrange multipliers can be used, find the dimen-sions. Compare your answer with that obtained inExercise 38, Section 13.9.
CAPSTONE
CAS
56. A can buoy is to be made of three pieces, namely, a cylinderand two equal cones, the altitude of each cone being equalto the altitude of the cylinder. For a given area of surface, what shape will have the greatest volume?
This problem was composed by the Committee on the Putnam Prize Competition.© The Mathematical Association of America. All rights reserved.
PUTNAM EXAM CHALLENGE
1053714_1310.qxp 10/27/08 12:10 PM Page 977
P!x, y" ! 100x0.6y0.4P!x, y" ! 100x0.25y0.75
P!x, y" ! 100x0.4y0.6P!x, y" ! 100x0.25y0.75
x " y ! a.
v2v1
#2#1
sin #1
v1!
sin #2
v2
x $ z ! 0.
n#x1 x2 x3 . . . xn ≤x1 " x2 " x3 " . . . " xn
n.
xi ≥ 0.. . . ! xn, $n
i!1xi ! S,
x1 ! x2 ! x3 !x1 x2 x3 . . . xn
3#xyz ≤x " y " z
3 .
In Exercises 33–42, use Lagrange multipliers to solve the indi-cated exercise in Section 13.9.
33. Exercise 1 34. Exercise 235. Exercise 5 36. Exercise 637. Exercise 9 38. Exercise 1039. Exercise 11 40. Exercise 1241. Exercise 17 42. Exercise 18
43. Maximum Volume Use Lagrange multipliers to find thedimensions of a rectangular box of maximum volume that canbe inscribed (with edges parallel to the coordinate axes) in theellipsoid
45. Minimum Cost A cargo container (in the shape of a rectangularsolid) must have a volume of 480 cubic feet. The bottom willcost $5 per square foot to construct and the sides and the topwill cost $3 per square foot to construct. Use Lagrangemultipliers to find the dimensions of the container of this sizethat has minimum cost.
46. Geometric and Arithmetic Means(a) Use Lagrange multipliers to prove that the product of three
positive numbers and whose sum has the constantvalue is a maximum when the three numbers are equal.Use this result to prove that
(b) Generalize the result of part (a) to prove that the productis a maximum when
and all Then prove that
This shows that the geometric mean is never greater thanthe arithmetic mean.
47. Minimum Surface Area Use Lagrange multipliers to find thedimensions of a right circular cylinder with volume cubicunits and minimum surface area.
48. Temperature Distribution Letrepresent the temperature at each point on the sphere
Find the maximum temperature on thecurve formed by the intersection of the sphere and the plane
49. Refraction of Light When light waves traveling in atransparent medium strike the surface of a second transparentmedium, they tend to “bend” in order to follow the path ofminimum time. This tendency is called refraction and isdescribed by Snell’s Law of Refraction,
where and are the magnitudes of the angles shown in thefigure, and and are the velocities of light in the two media.Use Lagrange multipliers to derive this law using
Figure for 49 Figure for 50
50. Area and Perimeter A semicircle is on top of a rectangle (seefigure). If the area is fixed and the perimeter is a minimum, orif the perimeter is fixed and the area is a maximum, useLagrange multipliers to verify that the length of the rectangle istwice its height.
Production Level In Exercises 51 and 52, find the maximumproduction level if the total cost of labor (at $72 per unit) andcapital (at $60 per unit) is limited to $250,000, where is thenumber of units of labor and is the number of units of capital.
51. 52.
Cost In Exercises 53 and 54, find the minimum cost ofproducing 50,000 units of a product, where is the numberof units of labor (at $72 per unit) and is the number of units ofcapital (at $60 per unit).
53. 54.
55. Investigation Consider the objective function subject to the constraint that , and are
the angles of a triangle.(a) Use Lagrange multipliers to maximize (b) Use the constraint to reduce the function to a function of
two independent variables. Use a computer algebra systemto graph the surface represented by Identify themaximum values on the graph.
g.
gg.
,cos cos cosg , ,
P x, y 100x0.6y0.4P x, y 100x0.25y0.75
yx
P x, y 100x0.4y0.6P x, y 100x0.25y0.75
yx
P
l
h
a
x
d1
y1θ
2θQ
d2
Medium 1
Medium 2
Px y a.
v2v1
21
sin 1
v1
sin 2
v2
x z 0.
x2 y2 z2 50.
T x, y, z 100 x2 y2
V0
n x1x2x3. . . xn
x1 x2 x3. . . xn
n .
xi 0.. . . xn,n
i 1xi S,
x1 x2 x3x1x2x3. . . xn
3 xyz x y z 3.S,
z,y,x,
x2 a2 y2 b2 z2 c2 1.
13.10 Lagrange Multipliers 977
44. The sum of the length and the girth (perimeter of a crosssection) of a package carried by a delivery service cannotexceed 108 inches.(a) Determine whether Lagrange multipliers can be used to
find the dimensions of the rectangular package oflargest volume that may be sent. Explain your reasoning.
(b) If Lagrange multipliers can be used, find the dimen-sions. Compare your answer with that obtained inExercise 38, Section 13.9.
CAPSTONE
CAS
56. A can buoy is to be made of three pieces, namely, a cylinderand two equal cones, the altitude of each cone being equalto the altitude of the cylinder. For a given area of surface, what shape will have the greatest volume?
This problem was composed by the Committee on the Putnam Prize Competition.© The Mathematical Association of America. All rights reserved.
PUTNAM EXAM CHALLENGE
1053714_1310.qxp 10/27/08 12:10 PM Page 977
Preparación del examen Putman56. Una boya está hecha de tres piezas, a saber, un cilindro y dos
conos iguales, la altura de cada uno de los conos es igual ala altura del cilindro. Para una superficie dada, ¿con quéforma se tendrá el volumen máximo?
Este problema fue preparado por el Committee on the Putnam Prize Competition. © The Mathematical Association of America. Todos los derechos reservados.
Para discusión44. La suma de las longitudes y el tamaño (perímetro de una sec-
ción transversal) de un paquete llevado por un servicio deentrega a domicilio no puede exceder 108 pulgadas. a) Determinar si los multiplicadores de Lagrange se pueden
usar para encontrar las dimensiones del paquete rectangu-lar de más grande volumen que puede ser enviado.Explicar el razonamiento.
b) Si se pueden usar los multiplicadores de Lagrange, encon-trar las dimensiones. Comparar su respuesta con la obteni-da en el ejercicio 38, sección 13.9.
sen sen
In Exercises 33–42, use Lagrange multipliers to solve the indi-cated exercise in Section 13.9.
33. Exercise 1 34. Exercise 235. Exercise 5 36. Exercise 637. Exercise 9 38. Exercise 1039. Exercise 11 40. Exercise 1241. Exercise 17 42. Exercise 18
43. Maximum Volume Use Lagrange multipliers to find thedimensions of a rectangular box of maximum volume that canbe inscribed (with edges parallel to the coordinate axes) in theellipsoid
45. Minimum Cost A cargo container (in the shape of a rectangularsolid) must have a volume of 480 cubic feet. The bottom willcost $5 per square foot to construct and the sides and the topwill cost $3 per square foot to construct. Use Lagrangemultipliers to find the dimensions of the container of this sizethat has minimum cost.
46. Geometric and Arithmetic Means(a) Use Lagrange multipliers to prove that the product of three
positive numbers and whose sum has the constantvalue is a maximum when the three numbers are equal.Use this result to prove that
(b) Generalize the result of part (a) to prove that the productis a maximum when
and all Then prove that
This shows that the geometric mean is never greater thanthe arithmetic mean.
47. Minimum Surface Area Use Lagrange multipliers to find thedimensions of a right circular cylinder with volume cubicunits and minimum surface area.
48. Temperature Distribution Letrepresent the temperature at each point on the sphere
Find the maximum temperature on thecurve formed by the intersection of the sphere and the plane
49. Refraction of Light When light waves traveling in atransparent medium strike the surface of a second transparentmedium, they tend to “bend” in order to follow the path ofminimum time. This tendency is called refraction and isdescribed by Snell’s Law of Refraction,
where and are the magnitudes of the angles shown in thefigure, and and are the velocities of light in the two media.Use Lagrange multipliers to derive this law using
Figure for 49 Figure for 50
50. Area and Perimeter A semicircle is on top of a rectangle (seefigure). If the area is fixed and the perimeter is a minimum, orif the perimeter is fixed and the area is a maximum, useLagrange multipliers to verify that the length of the rectangle istwice its height.
Production Level In Exercises 51 and 52, find the maximumproduction level if the total cost of labor (at $72 per unit) andcapital (at $60 per unit) is limited to $250,000, where is thenumber of units of labor and is the number of units of capital.
51. 52.
Cost In Exercises 53 and 54, find the minimum cost ofproducing 50,000 units of a product, where is the numberof units of labor (at $72 per unit) and is the number of units ofcapital (at $60 per unit).
53. 54.
55. Investigation Consider the objective function subject to the constraint that , and are
the angles of a triangle.(a) Use Lagrange multipliers to maximize (b) Use the constraint to reduce the function to a function of
two independent variables. Use a computer algebra systemto graph the surface represented by Identify themaximum values on the graph.
g.
gg.
,cos cos cosg , ,
P x, y 100x0.6y0.4P x, y 100x0.25y0.75
yx
P x, y 100x0.4y0.6P x, y 100x0.25y0.75
yx
P
l
h
a
x
d1
y1θ
2θQ
d2
Medium 1
Medium 2
Px y a.
v2v1
21
sin 1
v1
sin 2
v2
x z 0.
x2 y2 z2 50.
T x, y, z 100 x2 y2
V0
n x1x2x3. . . xn
x1 x2 x3. . . xn
n .
xi 0.. . . xn,n
i 1xi S,
x1 x2 x3x1x2x3. . . xn
3 xyz x y z 3.S,
z,y,x,
x2 a2 y2 b2 z2 c2 1.
13.10 Lagrange Multipliers 977
44. The sum of the length and the girth (perimeter of a crosssection) of a package carried by a delivery service cannotexceed 108 inches.(a) Determine whether Lagrange multipliers can be used to
find the dimensions of the rectangular package oflargest volume that may be sent. Explain your reasoning.
(b) If Lagrange multipliers can be used, find the dimen-sions. Compare your answer with that obtained inExercise 38, Section 13.9.
CAPSTONE
CAS
56. A can buoy is to be made of three pieces, namely, a cylinderand two equal cones, the altitude of each cone being equalto the altitude of the cylinder. For a given area of surface, what shape will have the greatest volume?
This problem was composed by the Committee on the Putnam Prize Competition.© The Mathematical Association of America. All rights reserved.
PUTNAM EXAM CHALLENGE
1053714_1310.qxp 10/27/08 12:10 PM Page 977
a
x
d1
y
2θ
1θ
Q
d2
Medio 1
Medio 2
P
l
h
In Exercises 33–42, use Lagrange multipliers to solve the indi-cated exercise in Section 13.9.
33. Exercise 1 34. Exercise 235. Exercise 5 36. Exercise 637. Exercise 9 38. Exercise 1039. Exercise 11 40. Exercise 1241. Exercise 17 42. Exercise 18
43. Maximum Volume Use Lagrange multipliers to find thedimensions of a rectangular box of maximum volume that canbe inscribed (with edges parallel to the coordinate axes) in theellipsoid
45. Minimum Cost A cargo container (in the shape of a rectangularsolid) must have a volume of 480 cubic feet. The bottom willcost $5 per square foot to construct and the sides and the topwill cost $3 per square foot to construct. Use Lagrangemultipliers to find the dimensions of the container of this sizethat has minimum cost.
46. Geometric and Arithmetic Means(a) Use Lagrange multipliers to prove that the product of three
positive numbers and whose sum has the constantvalue is a maximum when the three numbers are equal.Use this result to prove that
(b) Generalize the result of part (a) to prove that the productis a maximum when
and all Then prove that
This shows that the geometric mean is never greater thanthe arithmetic mean.
47. Minimum Surface Area Use Lagrange multipliers to find thedimensions of a right circular cylinder with volume cubicunits and minimum surface area.
48. Temperature Distribution Letrepresent the temperature at each point on the sphere
Find the maximum temperature on thecurve formed by the intersection of the sphere and the plane
49. Refraction of Light When light waves traveling in atransparent medium strike the surface of a second transparentmedium, they tend to “bend” in order to follow the path ofminimum time. This tendency is called refraction and isdescribed by Snell’s Law of Refraction,
where and are the magnitudes of the angles shown in thefigure, and and are the velocities of light in the two media.Use Lagrange multipliers to derive this law using
Figure for 49 Figure for 50
50. Area and Perimeter A semicircle is on top of a rectangle (seefigure). If the area is fixed and the perimeter is a minimum, orif the perimeter is fixed and the area is a maximum, useLagrange multipliers to verify that the length of the rectangle istwice its height.
Production Level In Exercises 51 and 52, find the maximumproduction level if the total cost of labor (at $72 per unit) andcapital (at $60 per unit) is limited to $250,000, where is thenumber of units of labor and is the number of units of capital.
51. 52.
Cost In Exercises 53 and 54, find the minimum cost ofproducing 50,000 units of a product, where is the numberof units of labor (at $72 per unit) and is the number of units ofcapital (at $60 per unit).
53. 54.
55. Investigation Consider the objective function subject to the constraint that , and are
the angles of a triangle.(a) Use Lagrange multipliers to maximize (b) Use the constraint to reduce the function to a function of
two independent variables. Use a computer algebra systemto graph the surface represented by Identify themaximum values on the graph.
g.
gg.
,cos cos cosg , ,
P x, y 100x0.6y0.4P x, y 100x0.25y0.75
yx
P x, y 100x0.4y0.6P x, y 100x0.25y0.75
yx
P
l
h
a
x
d1
y1θ
2θQ
d2
Medium 1
Medium 2
Px y a.
v2v1
21
sin 1
v1
sin 2
v2
x z 0.
x2 y2 z2 50.
T x, y, z 100 x2 y2
V0
n x1x2x3. . . xn
x1 x2 x3. . . xn
n .
xi 0.. . . xn,n
i 1xi S,
x1 x2 x3x1x2x3. . . xn
3 xyz x y z 3.S,
z,y,x,
x2 a2 y2 b2 z2 c2 1.
13.10 Lagrange Multipliers 977
44. The sum of the length and the girth (perimeter of a crosssection) of a package carried by a delivery service cannotexceed 108 inches.(a) Determine whether Lagrange multipliers can be used to
find the dimensions of the rectangular package oflargest volume that may be sent. Explain your reasoning.
(b) If Lagrange multipliers can be used, find the dimen-sions. Compare your answer with that obtained inExercise 38, Section 13.9.
CAPSTONE
CAS
56. A can buoy is to be made of three pieces, namely, a cylinderand two equal cones, the altitude of each cone being equalto the altitude of the cylinder. For a given area of surface, what shape will have the greatest volume?
This problem was composed by the Committee on the Putnam Prize Competition.© The Mathematical Association of America. All rights reserved.
PUTNAM EXAM CHALLENGE
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980 CAPÍTULO 13 Funciones de varias variables
Redacción En los ejercicios 69 y 70, redactar un párrafo brevesobre la superficie cuyas curvas de nivel (los valores de c espacia-dos uniformemente) se muestran. Hacer un comentario acerca delos posibles extremos, puntos silla, la magnitud del gradiente,etcétera.
69. 70.
71. Ganancia o beneficio máximo Una corporación fabrica, endos lugares, cámaras digitales. Las funciones de costo para pro-ducir unidades en el lugar 1 y unidades en el lugar 2 son
y la función del ingreso total es
Hallar los niveles de producción en los dos lugares que maxi-mizan el beneficio
72. Costo mínimo Un fabricante recibe una orden para 1 000unidades de bancos de madera que pueden producirse en doslugares. Sean y los números de unidades producidos encada uno de los dos lugares. La función del costo es
Hallar la cantidad que debe producirse en cada lugar para satis-facer la orden y minimizar el costo.
73. Nivel de producción La función de producción de un fabri-cante de dulces es
donde x es el número de unidades de trabajo y y es el número deunidades de capital. Suponer que la cantidad total disponiblepara trabajo y capital es $2 000, y que las unidades de trabajo ycapital cuestan $20 y $4, respectivamente. Hallar el nivel de pro-ducción máximo de este fabricante.
74. Hallar la distancia mínima del punto (2, 2, 0) a la superficie
75. Modelo matemático La tabla muestra la fuerza de fricción y enkilogramos de un vehículo de motor a las velocidades x, enkilómetros por hora, indicadas.
a) Utilizar el programa de regresión de una herramienta degraficación para hallar un modelo cuadrático de regresiónpor mínimos cuadrados para los datos.
b) Utilizar el modelo para estimar la fuerza total de fricción cuan-do el vehículo está en movimiento a 80 kilómetros por hora.
76. Modelo matemático Los datos en la tabla muestran el ren-dimiento y (en miligramos) en una reacción química después det minutos.
a) Utilizar el programa de regresión de una herramienta degraficación para hallar la recta de regresión de mínimoscuadrados para los datos. Después utilizar la herramienta degraficación para representar los datos y el modelo.
b) Utilizar una herramienta de graficación para trazar los pun-tos ¿Parecen seguir estos puntos un modelo linealcon más exactitud que los datos dados en el inciso a)?
c) Utilizar el programa de regresión de una herramienta de grafi-cación para hallar la recta de regresión de mínimos cuadradospara los puntos y obtener el modelo logarítmico
d) Utilizar una herramienta de graficación para representar losdatos y los modelos lineal y logarítmico. ¿Qué modelo esmejor? Explicar.
En los ejercicios 77 y 78, utilizar multiplicadores de Lagrangepara localizar y clasificar todos los extremos de la función.
77.
Restricción:78.
Restricción:
79. Costo mínimo Se va a construir un conducto para agua que vadel punto P al punto S y que debe atravesar por regiones dondelos costos de construcción difieren (ver la figura). El costo porkilómetro en dólares es 3k de P a Q, 2k de Q a R y k de R a S.Para simplificar, sea k = 1. Utilizar multiplicadores de Lagrangepara localizar x, y y z tales que el costo total C se minimice.
80. Investigación Considerar la función objetivo ƒ(x, y) ! ax "by sujeta a la restricción Suponer que y son positivas.a) Utilizar un sistema algebraico por computadora y representar
gráficamente la restricción o ligadura. Si y uti-lizar el sistema algebraico por computadora y representargráficamente las curvas de nivel de la función objetivo.Mediante ensayo y error, hallar la curva de nivel que pareceser tangente a la elipse. Utilizar el resultado para aproximarel máximo de f sujeto a la restricción o ligadura.
b) Repetir el inciso a) con y b ! 9.a ! 4
b ! 3,a ! 4
yxx2!64 " y2!36 ! 1.
1 km
P
Q
R Sx y z
10 km
2 km
x " 2y ! 2z ! x2y
x " y " z ! 1w ! xy " yz " xz
y ! a " b ln t."ln t, y#
"ln t, y#.
z ! x2 " y2.
f "x, y# ! 4x " xy " 2y
C ! 0.25x12 " 10x1 " 0.15x2
2 " 12x2.
x2x1
P"x1, x2# ! R # C1 # C2.
R ! $225 # 0.4"x1 " x2#%"x1 " x2#.
C2 ! 0.03x22 " 15x2 " 6100
C1 ! 0.05x12 " 15x1 " 5400
x2x1
x
y
x
y
Minutos, t 1 2 3 4
Rendimiento, y 1.2 7.1 9.9 13.1
Minutos, t 5 6 7 8
Rendimiento, y 15.5 16.0 17.9 18.0
Velocidad, x 25 50 75 100 125
Fuerza de fricción, y 24 34 50 71 98
5 4006 100
In Exercises 41– 44, find the indicated derivatives (a) usingthe appropriate Chain Rule and (b) using substitution beforedifferentiating.
41.
42.
43.
44.
In Exercises 45 and 46, differentiate implicitly to find the firstpartial derivatives of
45. 46.
In Exercises 47–50, find the directional derivative of the functionat in the direction of v.
47.
48.
49.
50.
In Exercises 51–54, find the gradient of the function and themaximum value of the directional derivative at the given point.
51. 52.
53. 54.
In Exercises 55 and 56, (a) find the gradient of the function at (b) find a unit normal vector to the level curve at (c) find the tangent line to the level curve at and(d) sketch the level curve, the unit normal vector, and the tangent line in the plane.
55. 56.
In Exercises 57–60, find an equation of the tangent plane andparametric equations of the normal line to the surface at thegiven point.
57.
58.
59.
60.
In Exercises 61 and 62, find symmetric equations of the tangentline to the curve of intersection of the surfaces at the givenpoint.
61.
62.
63. Find the angle of inclination of the tangent plane to thesurface at the point
64. Approximation Consider the following approximations for afunction centered at
[Note that the linear approximation is the tangent plane to thesurface at (a) Find the linear approximation of
centered at (b) Find the quadratic approximation of
centered at (c) If in the quadratic approximation, you obtain the
second-degree Taylor polynomial for what function?(d) Complete the table.
(e) Use a computer algebra system to graph the surfacesand How does the
accuracy of the approximations change as the distance fromincreases?
In Exercises 65–68, examine the function for relative extremaand saddle points. Use a computer algebra system to graph thefunction and confirm your results.
65.
66.
67.
68.
0.05y3 20.6y 125z 50 x y 0.1x3 20x 150
f x, y xy 1x
1y
f x, y x2 3xy y2 5xf x, y 2x2 6xy 9y2 8x 14
0, 0
z P2 x, y .z P1 x, y ,z f x, y ,
y 00, 0 .
f x, y cos x sen y0, 0 .
f x, y cos x sen y0, 0, f 0, 0 .
12 fxx 0, 0 x2 fxy 0, 0 xy 1
2 fyy 0, 0 y2
P2 x, y f 0, 0 fx 0, 0 x fy 0, 0 yQuadratic approximation:
P1 x, y f 0, 0 fx 0, 0 x fy 0, 0 yLinear approximation:
0, 0 .f x, y
2, 1, 3 .x2 y2 z2 14
2, 1, 3z x2 y2, z 32, 2, 5z 9 y2, y xPuntoSuperficies
1, 2, 2z 9 x2 y 2
2, 3, 4z 9 4x 6y x2 y2
2, 3, 4f x, y 25 y 2
2, 1, 4f x, y x2yPointSurface
c 3, P 2, 1c 65, P 3, 2
f x, y 4y sen x yf x, y 9x2 4y2
xy-
P,f x, y cP,f x, y cP,
z x2
x y , 2, 1z yx2 y2 , 1, 1
z e x cos y, 0, 4z x2y, 2, 1
v i j k1, 0, 1 ,w 5x2 2xy 3y2z,v 2i j 2k1, 2, 2 ,w y2 xz,
v 2i j1, 4 ,f x, y 14 y2 x2,
v 3i 4j5, 5 ,f x, y x2y,
P
xz2 y sen z 0x2 xy y2 yz z2 0
z.
z ty r sen t,x r cos t,
ur , u
tu x2 y2 z2,
z 2r ty rt,x 2r t,
wr , w
tw xyz ,
y sen tx cos t,
dudtu y2 x,
y 4 tx 2t,
dwdtw ln x2 y ,
Review Exercises 979
x y f x, y P1 x, y P2 x, y
0 0
0 0.1
0.2 0.1
0.5 0.3
1 0.5
SAC
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Solución de problemas 981
SP Solución de problemas
1. La fórmula de Heron establece que el área de un triángulo conlados de longitudes a, b y c está dada por
donde como se muestra en la figura.
a) Utilizar la fórmula de Heron para calcular el área del triángu-lo con vértices y
b) Mostrar que, de todos los triángulos que tienen un mismoperímetro, el triángulo con el área mayor es un triángulo equi-látero.
c) Mostrar que, de todos los triángulos que tienen una mismaárea, el triángulo con el perímetro menor es un triángulo equi-látero.
2. Un tanque industrial tiene forma cilíndrica con extremos he-misféricos, como se muestra en la figura. El depósito debe al-macenar 1 000 litros de fluido. Determinar el radio r y longitud hque minimizan la cantidad de material utilizado para laconstrucción del tanque.
3. Sea un punto en el primer octante en la superficie
a) Hallar la ecuación del plano tangente a la superficie en elpunto
b) Mostrar que el volumen del tetraedro formado en los tresplanos de coordenadas y el plano tangente es constante, inde-pendiente del punto de tangencia (ver la figura).
4. Utilizar un sistema algebraico por computadora y representar lasfunciones y en la misma pantalla.a) Mostrar que
y
b) Hallar el punto en la gráfica de f que está más alejado de lagráfica de g.
5. a) Sean f(x, y) = x – y y g(x, y) = x2 + y2 = 4. Graficar varias cur-vas de nivel de f y la restricción g en el plano xy. Usar la grá-fica para determinar el valor mayor de f sujeto a la restriccióng = 4. Después, verificar su resultado mediante los multipli-cadores de Lagrange.
b) Sean f(x, y) = x – y y g(x, y) = x2 + y2 = 0. Encontrar los valo-res máximos y mínimos de f sujetos a la restricción g = 0.¿Funcionará el método de los multiplicadores de Lagrange eneste caso? Explicar.
6. Un cuarto caliente de almacenamiento tiene la forma de una cajarectangular y un volumen de 1 000 pies cúbicos, como se mues-tra en la figura. Como el aire caliente sube, la pérdida de calorpor unidad de área a través del techo es cinco veces mayor quela pérdida de calor a través del suelo. La pérdida de calor através de las cuatro paredes es tres veces mayor que la pérdi-da de calor a través del suelo. Determinar las dimensiones delcuarto que minimizan la pérdida de calor y que por consi-guiente minimizan los costos de calefacción.
7. Repetir el ejercicio 6 suponiendo que la pérdida de calor a travésde las paredes y del techo sigue siendo la misma, pero el suelose aísla de manera que no hay ninguna pérdida de calor a travésdel mismo.
8. Considerar una placa circular de radio 1 dada por como se muestra en la figura. La temperatura sobre cualquierpunto de la placa es
a) Dibujar las isotermas b) Hallar el punto más caliente y el punto más frío de la placa.
9. Considerar la función de producción de Cobb-Douglas
a) Mostrar que satisface la ecuación
b) Mostrar que .
10. Expresar la ecuación de Laplace en coor-
denadas cilíndricas.
!2u!x2 "
!2u!y2 "
!2u!z2 # 0
f !tx, ty" # t f !x, y"
x !fdx
" y !fdy
# f.f
0 < a < 1.f !x, y" # Cxay1$a,
T!x, y" # 10.
x1−1
−1
1x2 + y2 ≤ 1
y
T!x, y" # 2x2 " y2 $ y " 10.P!x, y"
x2 " y2 ≤ 1,
z
xy
V = xyz = 1 000
limx→$%
# f !x" $ g!x"$ # 0.limx→%
# f !x" $ g!x"$ # 0
g!x" # xf !x" # 3%x3 $ 1
y
x
3
3
3
z
P
P.
xyz # 1.P!x0, y0, z0"
h
r
!6, 0".!3, 4",!0, 0",
a b
c
s #a " b " c
2 ,
A # %s!s $ a"!s $ b"!s $ c"
lím lím
Larson-13-11-R.qxd 3/12/09 19:28 Page 981
SECCIÓN 13.9 Aplicaciones de los extremos de funciones de dos variables 967
12. Volumen máximo Mostrar que la caja rectangular de volumenmáximo inscrita en una esfera de radio r es un cubo.
13. Volumen y área exterior Mostrar que una caja rectangular devolumen dado y área exterior mínima es un cubo.
14. Área Un comedero de secciones transversales en forma detrapecio se forma doblando los extremos de una lámina de alu-minio de 30 pulgadas de ancho (ver la figura). Hallar la seccióntransversal de área máxima.
15. Ingreso máximo Una empresa fabrica dos tipos de zapatostenis, tenis para correr y tenis para baloncesto. El ingreso total de
unidades de tenis para correr y unidades de tenis de balon-cesto es donde y están en miles de unidades. Hallar las y que maximizanel ingreso.
16. Ganancia o beneficio máximo Una empresa fabrica velas endos lugares. El costo de producción de unidades en el lugar 1es
y el costo de producción de x2 unidades en el lugar 2 es
Las velas se venden a $15 por unidad. Hallar la cantidad quedebe producirse en cada lugar para aumentar al máximo el be-neficio
17. Ley de Hardy-Weinberg Los tipos sanguíneos son genética-mente determinados por tres alelos A, B y O. (Alelo escualquiera de las posibles formas de mutación de un gen.) Unapersona cuyo tipo sanguíneo es AA, BB u OO es homocigótica.Una persona cuyo tipo sanguíneo es AB, AO o BO es hetero-cigótica. La ley Hardy-Weinberg establece que la proporción Pde individuos heterocigótica en cualquier población dada es
donde p representa el porcentaje de alelos A en la población, qrepresenta el porcentaje de alelos B en la población y r repre-senta el porcentaje de alelos O en la población. Utilizar el hechode que para mostrar que la proporción máxi-ma de individuos heterocigóticos en cualquier población es
18. Índice de diversidad de Shannon Una forma de medir diversi-dad de especies es usar el índice de diversidad de Shannon H. Siun hábitat consiste de tres especies, A, B y C, su índice de diver-sidad de Shannon es
donde x es el porcentaje de especies A en el hábitat, y es el por-centaje de especies B en el hábitat y z es el porcentaje deespecies C en el hábitat.a) Usar el factor de x + y + z = 1 para demostrar que el valor
máximo de H ocurre cuando b) Usar el resultado del inciso a) para demostrar que el valor
máximo de H en este hábitat es de ln 3.
19. Costo mínimo Hay que construir un conducto para agua desdeel punto P al punto S y debe atravesar regiones donde los costosde construcción difieren (ver la figura). El costo por kilómetroen dólares es 3k de P a Q, 2k de Q a R y k de R a S. Hallar x y ytales que el costo total C se minimice.
20. Distancia Una empresa tiene tres tiendas de ventas al menudeolocalizadas en los puntos (0, 0), (2, 2) y (!2, 2) (ver la figura). Ladirección planea construir un centro de distribución localizado detal manera que la suma S de las distancias del centro a las tiendassea mínimo. Por la simetría del problema es claro que el centro dedistribución se localizará en el eje y, y por consiguiente S es unafunción de una variable y. Utilizando las técnicas presentadas en elcapítulo 3, calcular el valor de y requerido.
Figura para 20 Figura para 21
21. Investigación Las tiendas de ventas al menudeo descritas en elejercicio 20 se localizan en (0, 0), (4, 2) y (!2, 2) (ver la figura).La localización del centro de distribución es (x, y), y por consi-guiente la suma S de las distancias es una función de x y y.a) Escribir la expresión que da la suma S de las distancias.
Utilizar un sistema algebraico por computadora y representarS. ¿Tiene esta superficie un mínimo?
b) Utilizar un sistema algebraico por computadora y obtener y Observar que resolver el sistema y es muydifícil. Por tanto, aproximar la localización del centro de dis-tribución.
c) Una estimación inicial del punto crítico es Calcular con componentes y ¿Qué dirección es la dada por el vector
d) La segunda estimación del punto crítico es
Si se sustituyen estas coordenadas en entonces S seconvierte en una función de una variable t. Hallar el valor det que minimiza S. Utilizar este valor de t para estimar
e) Realizar dos iteraciones más del proceso del inciso d) paraobtener Dada esta localización del centro de dis-tribución, ¿cuál es la suma de las distancias a las tiendas almenudeo?
f) Explicar por qué se usó para aproximar el valormínimo de S. ¿En qué tipo de problemas se usaría !S!x, y"?
"!S!x, y"
!x4, y4".
!x2, y2".
S!x, y",!x2, y2" # !x1 " Sx!x1, y1"t, y1 " Sy!x1, y1"t".
"!S!1, 1"?"Sy!1, 1"."Sx!1, 1""!S!1, 1"
!x1, y1" # !1, 1".
Sy # 0Sx # 0Sy.Sx
x2 4
4
−2
−2
(−2, 2) (4, 2)
(0, 0)
(x, y)d1 d2
d3
y
x−3
−2
−2
3
2
21
(2, 2)(−2, 2)
(0, y)d1
d2
d3
(0, 0)
y
1 km
P
Q
R
S
x
y
10 km
2 km
12. Maximum Volume Show that the rectangular box of maxi-mum volume inscribed in a sphere of radius is a cube.
13. Volume and Surface Area Show that a rectangular box ofgiven volume and minimum surface area is a cube.
14. Area A trough with trapezoidal cross sections is formed byturning up the edges of a 30-inch-wide sheet of aluminum (seefigure). Find the cross section of maximum area.
15. Maximum Revenue A company manufactures two types ofsneakers, running shoes and basketball shoes. The total revenuefrom units of running shoes and units of basketball shoesis where and
are in thousands of units. Find and so as to maximizethe revenue.
16. Maximum Profit A corporation manufactures candles at twolocations. The cost of producing units at location 1 is
and the cost of producing units at location 2 is
The candles sell for $15 per unit. Find the quantity that shouldbe produced at each location to maximize the profit
17. Hardy-Weinberg Law Common blood types are determinedgenetically by three alleles A, B, and O. (An allele is any of agroup of possible mutational forms of a gene.) A person whoseblood type is AA, BB, or OO is homozygous. A person whoseblood type is AB, AO, or BO is heterozygous. The Hardy-Weinberg Law states that the proportion of heterozygousindividuals in any given population is
where represents the percent of allele A in the population,represents the percent of allele B in the population, and represents the percent of allele O in the population. Use the factthat to show that the maximum proportion ofheterozygous individuals in any population is
18. Shannon Diversity Index One way to measure species diver-sity is to use the Shannon diversity index If a habitat consistsof three species, A, B, and C, its Shannon diversity index is
where is the percent of species A in the habitat, is the percent of species B in the habitat, and is the percent ofspecies C in the habitat.(a) Use the fact that to show that the maximum
value of occurs when (b) Use the results of part (a) to show that the maximum value
of in this habitat is
19. Minimum Cost A water line is to be built from point topoint and must pass through regions where construction costsdiffer (see figure). The cost per kilometer in dollars is from
to from to and from to Find and suchthat the total cost will be minimized.
20. Distance A company has retail outlets located at the pointsand (see figure). Management plans to
build a distribution center located such that the sum of thedistances from the center to the outlets is minimum. From thesymmetry of the problem it is clear that the distribution centerwill be located on the axis, and therefore is a function of thesingle variable Using techniques presented in Chapter 3, findthe required value of
Figure for 20 Figure for 21
21. Investigation The retail outlets described in Exercise 20 arelocated at and (see figure). The locationof the distribution center is and therefore the sum of thedistances is a function of and (a) Write the expression giving the sum of the distances Use
a computer algebra system to graph Does the surfacehave a minimum?
(b) Use a computer algebra system to obtain and Observethat solving the system and is very difficult.So, approximate the location of the distribution center.
(c) An initial estimate of the critical point is Calculate with components and
What direction is given by the vector (d) The second estimate of the critical point is
If these coordinates are substituted into then becomes a function of the single variable Find the valueof that minimizes Use this value of to estimate
(e) Complete two more iterations of the process in part (d) toobtain For this location of the distribution center,what is the sum of the distances to the retail outlets?
(f) Explain why was used to approximate theminimum value of In what types of problems would youuse S x, y ?
S.S x, y
x4, y4 .
x2, y2 .tS.tt.
SS x, y ,
x2, y2 x1 Sx x1, y1 t, y1 Sy x1, y1 t .
S 1, 1 ?Sy 1, 1 .Sx 1, 1S 1, 1
x1, y1 1, 1 .
Sy 0Sx 0Sy.Sx
S.S.
y.xSx, y ,
2, 24, 2 ,0, 0 ,
2 4
4
−2
−2
(−2, 2) (4, 2)
(0, 0)
(x, y)d2 d1
d3
y
−3
−2
−2
32
21
(2, 2)(−2, 2)
(0, y)d1
d2
d3
(0, 0)
y
y.y.
Sy-
S
2, 22, 2 ,0, 0 ,
1 km
P
Q
R
S
x
y
10 km
2 km
CyxS.RkR,Q2kQ,P
3kS
P
ln 3.H
x y z 13.H
x y z 1
zyx
H x ln x y ln y z ln z
H.
23.
p q r 1
rqp
P p, q, r 2pq 2pr 2qr
P
P 15 x1 x2 C1 C2.
C2 0.05x22 4x2 275.
x2
C1 0.02x12 4x1 500
x1
x2x1x2
x1R 5x12 8x2
2 2x1x2 42x1 102x2,x2x1
30 − 2x
x x
θθ
r
13.9 Applications of Extrema of Functions of Two Variables 967
CAS
1053714_1309.qxp 10/27/08 12:10 PM Page 967
23.
p $ q $ r # 1
P! p, q, r" # 2pq $ 2pr $ 2qr
P # 15!x1 $ x2" " C1 " C2.
C2 # 0.05x22 $ 4x2 $ 275.
C1 # 0.02x12 $ 4x1 $ 500
x1
x2x1x2
x1R # "5x12 " 8x2
2 " 2x1x2 $ 42x1 $ 102x2,x2x1
30 − 2x
x x
θθ
12. Maximum Volume Show that the rectangular box of maxi-mum volume inscribed in a sphere of radius is a cube.
13. Volume and Surface Area Show that a rectangular box ofgiven volume and minimum surface area is a cube.
14. Area A trough with trapezoidal cross sections is formed byturning up the edges of a 30-inch-wide sheet of aluminum (seefigure). Find the cross section of maximum area.
15. Maximum Revenue A company manufactures two types ofsneakers, running shoes and basketball shoes. The total revenuefrom units of running shoes and units of basketball shoesis where and
are in thousands of units. Find and so as to maximizethe revenue.
16. Maximum Profit A corporation manufactures candles at twolocations. The cost of producing units at location 1 is
and the cost of producing units at location 2 is
The candles sell for $15 per unit. Find the quantity that shouldbe produced at each location to maximize the profit
17. Hardy-Weinberg Law Common blood types are determinedgenetically by three alleles A, B, and O. (An allele is any of agroup of possible mutational forms of a gene.) A person whoseblood type is AA, BB, or OO is homozygous. A person whoseblood type is AB, AO, or BO is heterozygous. The Hardy-Weinberg Law states that the proportion of heterozygousindividuals in any given population is
where represents the percent of allele A in the population,represents the percent of allele B in the population, and represents the percent of allele O in the population. Use the factthat to show that the maximum proportion ofheterozygous individuals in any population is
18. Shannon Diversity Index One way to measure species diver-sity is to use the Shannon diversity index If a habitat consistsof three species, A, B, and C, its Shannon diversity index is
where is the percent of species A in the habitat, is the percent of species B in the habitat, and is the percent ofspecies C in the habitat.(a) Use the fact that to show that the maximum
value of occurs when (b) Use the results of part (a) to show that the maximum value
of in this habitat is
19. Minimum Cost A water line is to be built from point topoint and must pass through regions where construction costsdiffer (see figure). The cost per kilometer in dollars is from
to from to and from to Find and suchthat the total cost will be minimized.
20. Distance A company has retail outlets located at the pointsand (see figure). Management plans to
build a distribution center located such that the sum of thedistances from the center to the outlets is minimum. From thesymmetry of the problem it is clear that the distribution centerwill be located on the axis, and therefore is a function of thesingle variable Using techniques presented in Chapter 3, findthe required value of
Figure for 20 Figure for 21
21. Investigation The retail outlets described in Exercise 20 arelocated at and (see figure). The locationof the distribution center is and therefore the sum of thedistances is a function of and (a) Write the expression giving the sum of the distances Use
a computer algebra system to graph Does the surfacehave a minimum?
(b) Use a computer algebra system to obtain and Observethat solving the system and is very difficult.So, approximate the location of the distribution center.
(c) An initial estimate of the critical point is Calculate with components and
What direction is given by the vector (d) The second estimate of the critical point is
If these coordinates are substituted into then becomes a function of the single variable Find the valueof that minimizes Use this value of to estimate
(e) Complete two more iterations of the process in part (d) toobtain For this location of the distribution center,what is the sum of the distances to the retail outlets?
(f) Explain why was used to approximate theminimum value of In what types of problems would youuse S x, y ?
S.S x, y
x4, y4 .
x2, y2 .tS.tt.
SS x, y ,
x2, y2 x1 Sx x1, y1 t, y1 Sy x1, y1 t .
S 1, 1 ?Sy 1, 1 .Sx 1, 1S 1, 1
x1, y1 1, 1 .
Sy 0Sx 0Sy.Sx
S.S.
y.xSx, y ,
2, 24, 2 ,0, 0 ,
2 4
4
−2
−2
(−2, 2) (4, 2)
(0, 0)
(x, y)d2 d1
d3
y
−3
−2
−2
32
21
(2, 2)(−2, 2)
(0, y)d1
d2
d3
(0, 0)
y
y.y.
Sy-
S
2, 22, 2 ,0, 0 ,
1 km
P
Q
R
S
x
y
10 km
2 km
CyxS.RkR,Q2kQ,P
3kS
P
ln 3.H
x y z 13.H
x y z 1
zyx
H x ln x y ln y z ln z
H.
23.
p q r 1
rqp
P p, q, r 2pq 2pr 2qr
P
P 15 x1 x2 C1 C2.
C2 0.05x22 4x2 275.
x2
C1 0.02x12 4x1 500
x1
x2x1x2
x1R 5x12 8x2
2 2x1x2 42x1 102x2,x2x1
30 − 2x
x x
θθ
r
13.9 Applications of Extrema of Functions of Two Variables 967
CAS
1053714_1309.qxp 10/27/08 12:10 PM Page 967
12. Maximum Volume Show that the rectangular box of maxi-mum volume inscribed in a sphere of radius is a cube.
13. Volume and Surface Area Show that a rectangular box ofgiven volume and minimum surface area is a cube.
14. Area A trough with trapezoidal cross sections is formed byturning up the edges of a 30-inch-wide sheet of aluminum (seefigure). Find the cross section of maximum area.
15. Maximum Revenue A company manufactures two types ofsneakers, running shoes and basketball shoes. The total revenuefrom units of running shoes and units of basketball shoesis where and
are in thousands of units. Find and so as to maximizethe revenue.
16. Maximum Profit A corporation manufactures candles at twolocations. The cost of producing units at location 1 is
and the cost of producing units at location 2 is
The candles sell for $15 per unit. Find the quantity that shouldbe produced at each location to maximize the profit
17. Hardy-Weinberg Law Common blood types are determinedgenetically by three alleles A, B, and O. (An allele is any of agroup of possible mutational forms of a gene.) A person whoseblood type is AA, BB, or OO is homozygous. A person whoseblood type is AB, AO, or BO is heterozygous. The Hardy-Weinberg Law states that the proportion of heterozygousindividuals in any given population is
where represents the percent of allele A in the population,represents the percent of allele B in the population, and represents the percent of allele O in the population. Use the factthat to show that the maximum proportion ofheterozygous individuals in any population is
18. Shannon Diversity Index One way to measure species diver-sity is to use the Shannon diversity index If a habitat consistsof three species, A, B, and C, its Shannon diversity index is
where is the percent of species A in the habitat, is the percent of species B in the habitat, and is the percent ofspecies C in the habitat.(a) Use the fact that to show that the maximum
value of occurs when (b) Use the results of part (a) to show that the maximum value
of in this habitat is
19. Minimum Cost A water line is to be built from point topoint and must pass through regions where construction costsdiffer (see figure). The cost per kilometer in dollars is from
to from to and from to Find and suchthat the total cost will be minimized.
20. Distance A company has retail outlets located at the pointsand (see figure). Management plans to
build a distribution center located such that the sum of thedistances from the center to the outlets is minimum. From thesymmetry of the problem it is clear that the distribution centerwill be located on the axis, and therefore is a function of thesingle variable Using techniques presented in Chapter 3, findthe required value of
Figure for 20 Figure for 21
21. Investigation The retail outlets described in Exercise 20 arelocated at and (see figure). The locationof the distribution center is and therefore the sum of thedistances is a function of and (a) Write the expression giving the sum of the distances Use
a computer algebra system to graph Does the surfacehave a minimum?
(b) Use a computer algebra system to obtain and Observethat solving the system and is very difficult.So, approximate the location of the distribution center.
(c) An initial estimate of the critical point is Calculate with components and
What direction is given by the vector (d) The second estimate of the critical point is
If these coordinates are substituted into then becomes a function of the single variable Find the valueof that minimizes Use this value of to estimate
(e) Complete two more iterations of the process in part (d) toobtain For this location of the distribution center,what is the sum of the distances to the retail outlets?
(f) Explain why was used to approximate theminimum value of In what types of problems would youuse S x, y ?
S.S x, y
x4, y4 .
x2, y2 .tS.tt.
SS x, y ,
x2, y2 x1 Sx x1, y1 t, y1 Sy x1, y1 t .
S 1, 1 ?Sy 1, 1 .Sx 1, 1S 1, 1
x1, y1 1, 1 .
Sy 0Sx 0Sy.Sx
S.S.
y.xSx, y ,
2, 24, 2 ,0, 0 ,
2 4
4
−2
−2
(−2, 2) (4, 2)
(0, 0)
(x, y)d2 d1
d3
y
−3
−2
−2
32
21
(2, 2)(−2, 2)
(0, y)d1
d2
d3
(0, 0)
y
y.y.
Sy-
S
2, 22, 2 ,0, 0 ,
1 km
P
Q
R
S
x
y
10 km
2 km
CyxS.RkR,Q2kQ,P
3kS
P
ln 3.H
x y z 13.H
x y z 1
zyx
H x ln x y ln y z ln z
H.
23.
p q r 1
rqp
P p, q, r 2pq 2pr 2qr
P
P 15 x1 x2 C1 C2.
C2 0.05x22 4x2 275.
x2
C1 0.02x12 4x1 500
x1
x2x1x2
x1R 5x12 8x2
2 2x1x2 42x1 102x2,x2x1
30 − 2x
x x
θθ
r
13.9 Applications of Extrema of Functions of Two Variables 967
CAS
1053714_1309.qxp 10/27/08 12:10 PM Page 967
Larson-13-09.qxd 3/12/09 19:18 Page 967
A-44 Soluciones de los ejercicios impares
b)
c)
d)e)f ) da la dirección de la máxima tasa de decrecimiento
23. Expresar la ecuación a maximizar o minimizar como una funciónde dos variables. Tomar las derivadas parciales e igualarlas a ceroo indefinido para obtener los puntos críticos. Utilizar el criterio delas segundas derivadas parciales para extremos relativos utilizan-do los puntos críticos. Verificar los puntos frontera.
25. a) b) 27. a) b) 229. 31.
33. a)b) c) 1.6
35.41.4 bushels por acre
37.
39. 41.
43. a)
b)
45. a) b)c) d) Demostración
47. Demostración
Sección 13.10 (página 976)1. 3.
5. 7.9. 11. 13.
15. Máximos:
Mínimos:
17. 19. 21. 23.25. 0.188 27. 29.31. Los problemas de optimización que tienen restricciones sobre los
valores que pueden ser usados para producir las soluciones ópti-mas se conocen como problemas de optimización restringidos.
33. 35.37. $26.73 39.41. Demostración 43.45. pies
47. y 49. Demostración
51.53.
55. a)b)
Los valores máximos ocurren cuando .
3
3
2
3
g 3, 3, 3 18
Costo $55 095.60 y 688.7 x 191.3
P 15 625 18, 3 125 226 869
h 2 3v0
2r 3v0
2
3 360 3 360 43 3 360
2 3a 3 2 3b 3 2 3c 3a b c k 39 pies 9 pies 8.25 pies;
x y z 33
4, 0, 4311 23 22 2f 8, 16, 8 1024
f 2 2, 2 2 12
f 2 2, 2 2 12
f 2 2, 2 2 52
f 2 2, 2 2 52
f 13, 13, 13
13f 3, 3, 3 27f 1, 1 2
f 25, 50 2 600f 1, 2 5f 2, 2 8f 5, 5 25
x
4
44
4
Restricción
y
Curvas de nivel2
2
4
4
6
6
8
8
10
10
12
12
xRestricción
Curvas de nivel
y
2 24
2,000
14,000
P 10,957.7e 0.1499hln P 0.1499h 9.3018
1 14
20
120
y 0.22x2 9.66x 1.79
5
2
7(0, 0)(2, 2)
(3, 6)
(4, 12)
14
2
69( 2, 0)
( 1, 0)
(0, 1)
(1, 2)
(2, 5)
8
y x2 xy 37 x2 6
5 x2635
an
i 1 xi2 b
n
i 1 xi cn
n
i 1 yi
an
i 1 xi3 b
n
i 1 xi2 c
n
i 1 xi
n
i 1 xi yi
an
i 1 xi4 b
n
i 1 xi3 c
n
i 1 xi2
n
i 1 xi2 yi
y 14x 19
050
250
80
y 1.6x 84
4 18
6
(0, 6)
(4, 3)
(5, 0)(8, 4) (10, 5)
y = x +175148
945148
8
2 10
1
7
(0, 0)(1, 1)
(4, 2)
(3, 4)(5, 5)
y x= +37 743 43
y 175148 x 945
148y 3743 x 7
43
y 2x 416y 3
4 x 43
S x, yS x, y
S 7.266x4, y4 0.06, 0.45 ;x2, y2 0.05, 0.90t 1.344;
186.0
12
i 12
210j
y 2x 4 2 y 2 2
Syy
x2 y 2y 2
x 2 2 y 2 2
x 4x 4 2 y 2 2
Sxx
x2 y2x 2
x 2 2 y 2 2
Answers to Odd-Numbered Exercises A137
de S. Usar para encontrar un máximo.
Soluciones_Vol_2.indd 44 3/12/09 20:38:24
A-46 Soluciones de los ejercicios impares
71. 73.75. a) b) 50.6 kg77. Máximo:79.
SP Solución de problemas (página 981)1. a) 12 unidades cuadradas b) Demostración c) Demostración3. a)b)
Entonces el plano tangente es
Intersecciones:
5. a) b)
Valor máximo: Valores máximo y mínimo: 0El método de los multiplicado-res de Lagrange no se aplicaporque
7.
9. a)
b)
11. a)
b)
c)
d)No; la razón de cambio de esmayor cuando el proyectil estámás cerca de la cámara.
e) es máximo cuando segundos.No; el proyectil alcanza su máxima altura cuando
segundos.
13. a) b)
Mínimo: Mínimos:Máximos: Máximos:Puntos silla: Puntos silla:
c)Mínimo: Mínimos:Máximos: Máximos:Puntos silla: Puntos silla:
15. a)
b)
c) Alturad)
17 a 19. Demostraciones
Capítulo 14Sección 14.1 (página 990)
1. 3. 5.7. 9. 11. 3
13. 15. 17. 2 19. 21. 1 629 23. 25. 427. 29. 31. 33. Diverge 35. 2437. 39. 41. 5 43. 45.47. 49.
51. 53.
1
0
y
y f x, y dx dy
ln 10
0
10
ex f x, y dy dx
x− 2 − 1 1 2
2
3
4
y
1
2
4
6
8
2 3
y
x
2
0
4 y2
4 y2 f x, y dx dy
4
0
4
x f x, y dy dx
−2 −1 1 2
−1
3
1
y
x
1 2 3 4
1
2
3
x
y
92ab8
3163
12
2 32 182
23
13
12
83
x2(1 e x2 x2e x2y 2 ln y 2 y24x2 x 4 2y ln 2y2x2
dl 0, dh 0.01: dA 0.06dl 0.01, dh 0: dA 0.01
1 cm
6 cm
1 cm
6 cm±1, 0, e 1
0, 0, 00, ±1, e 10, ±1, e 1±1, 0, e 10, 0, 0
< 0 > 00, 0, 0±1, 0, e 1
0, ±1, 2e 10, ±1, 2e 1±1, 0, e 10, 0, 0
x
y12
−1
1
z
x
y
1
22
z
t 21.41
t 0.98
0 4
−5
30
ddt
16 8 2 t 2 25t 25 264t4 256 2 t3 1024t2 800 2 t 625
arctan 32 2 t 16t2
32 2 t 50 arctan y
x 50
y 32 2t 16t 2x 32 2t
tf x, y tCxay1 a Ctxay1 a
C tx a ty 1 af tx, ty f x, y Cxay1 a Cxay1 a a 1 a axaCy1 a 1 a xaC y1 a
xCy1 aaxa 1 yCxa 1 a y1 a 1x fx y f
y
2 3 150 2 3 150 5 3 150 3
g x0, y0 0.
2 2
y
x32 41−1−2
−3
−2
−4
−1
1
2
k = 2k = 1k = 0
k = 3
g(x, y)
y
x3 411
3
4
1
1
k = 2k = 1k = 0
k = 3
g(x, y)
V 13 bh 9
2
3x0, 0, 0 , 0, 3y0, 0 , 0, 0, 3x0 y0
y01
x0 y0x x0 x0
1x0 y0
y y0 x0 y0 z 1x0 y0
0.
z0 1 x0 y0 x0 y0z0 1y0z0 x x0 x0z0 y y0 x0 y0 z z0 0
z 60 3 2 2 3 6 8.716 kmy 3 3 0.577 km;x 2 2 0.707 km;
f 13, 13, 13
13
y 0.004x2 0.07x 19.4f 49.4, 253 13 201.8x1 94, x2 157
Answers to Odd-Numbered Exercises A139
1053714_ans_14.qxp 10/27/08 3:59 PM Page A139
Soluciones_Vol_2.indd 46 3/12/09 20:38:31
Soluciones de los ejercicios impares A-43
17. 19.
Máximo relativo: Mínimo relativo: Mínimo relativo: Máximos relativos:
Puntos silla:21. Máximo relativo: 23. Puntos silla: 25. Puntos silla:27. No hay números críticos.29. nunca es negativo. Mínimo: cuando
31. Información insuficiente. 33. Punto silla.35.37. a) b) Punto silla. c)
d)
39. a) b) Mínimos absolutos:c) d)
41. a) b) Mínimo absoluto: c)d)
43. Mínimo relativo:45. Máximo absoluto:
Mínimo absoluto:47. Máximo absoluto:
Mínimo absoluto:49. Máximos absolutos:
Mínimo absoluto:51. Máximos absolutos:
Mínimos absolutos:53. Máximo absoluto:
Mínimo absoluto:55. El punto A es un punto silla.57. Las respuestas varían.
Ejemplo de respuesta:59. Las respuestas varían.
Ejemplo de respuesta:
No hay extremos Punto silla61. Falso. Sea en el punto63. Falso. Sea (ver ejemplo 4 de la página 958).
Sección 13.9 (página 966)1. 3. 5. 7. 10, 10, 109. $26.73
11. Sea
Así, y Por tanto,13. Sean x, y y z la longitud, ancho y altura, respectivamente, y sea V
el volumen dado. Entonces El área de lasuperficie es
Así,15. 17. Demostración19. km
21. a)
La superficie tiene un mínimo.
xy
468
24
20
4
22 4 6 8
S
x 4 2 y 2 2 S x2 y 2 x 2 2 y 2 2
y 3 2 2 3 6 1.284 kmx 2 2 0.707x1 3; x2 6
x 3 V0, y 3 V0, y z 3 V0.
Sx 2 y V0 x2 0 x2y V0 0Sy 2 x V0 y2 0 xy2 V0 0
S 2xy 2yz 2xz 2 xy V0 x V0 y .
a b c k 3.b k 3.a b
Va43 kb 2ab b2
Vb43 ka a2 2ab
0
0
kb 2ab b2
kb a2 2ab
0
0
V 4 abc 3 43 ab k a b 4
3 kab a2b ab2a b c k.
9 pies 9 pies 8.25 pies;x y z 373
f x, y x2y20, 0, 1 .f x, y 1 x y
xy
67
−3
36
z
x
y
2
30
45
60
75
2
z
0, 0, 01, 1, 1x, x, 0 , x 1
2, 1, 9 , 2, 1, 90, 1, 2
±2, 4, 281, 2, 50, 1, 104, 2, 114, 0, 21
0, 3, 1
4 26
xy
2 4 6
z
6
Mínimo absoluto (0, 0, 0)
0, 00, 0, 00, 0
42
6
x
y
−4
−2
4
z
6
Mínimoabsoluto(1, a, 0)
Mínimoabsoluto(b, −4, 0)
1, a , b, 41, a, 0 , b, 4, 01, a , b, 4
x
y
−2
−2
−22
21
z
2
Punto silla(0, 0, 0)
0, 00, 0, 00, 04 < fxy 3, 7 < 4
z
yx3
3
40
60
x y 0.z 0z
1, 1, 10, 0, 040, 40, 3 200
±1, 0, 10, ±1, 41, 0, 2
0, 0, 01, 0, 2
−4
44
−4
56
yx
z
x
y
5
−4
−4
4
4
z
A136 Answers to Odd-Numbered Exercises
y z V0 xy.V0 xyz0
Soluciones_Vol_2.indd 43 3/12/09 20:38:22
Soluciones de los ejercicios impares A-43
17. 19.
Máximo relativo: Mínimo relativo: Mínimo relativo: Máximos relativos:
Puntos silla:21. Máximo relativo: 23. Puntos silla: 25. Puntos silla:27. No hay números críticos.29. nunca es negativo. Mínimo: cuando
31. Información insuficiente. 33. Punto silla.35.37. a) b) Punto silla. c)
d)
39. a) b) Mínimos absolutos:c) d)
41. a) b) Mínimo absoluto: c)d)
43. Mínimo relativo:45. Máximo absoluto:
Mínimo absoluto:47. Máximo absoluto:
Mínimo absoluto:49. Máximos absolutos:
Mínimo absoluto:51. Máximos absolutos:
Mínimos absolutos:53. Máximo absoluto:
Mínimo absoluto:55. El punto A es un punto silla.57. Las respuestas varían.
Ejemplo de respuesta:59. Las respuestas varían.
Ejemplo de respuesta:
No hay extremos Punto silla61. Falso. Sea en el punto63. Falso. Sea (ver ejemplo 4 de la página 958).
Sección 13.9 (página 966)1. 3. 5. 7. 10, 10, 109. $26.73
11. Sea
Así, y Por tanto,13. Sean x, y y z la longitud, ancho y altura, respectivamente, y sea V
el volumen dado. Entonces El área de lasuperficie es
Así,15. 17. Demostración19. km
21. a)
La superficie tiene un mínimo.
xy
468
24
20
4
22 4 6 8
S
x 4 2 y 2 2 S x2 y 2 x 2 2 y 2 2
y 3 2 2 3 6 1.284 kmx 2 2 0.707x1 3; x2 6
x 3 V0, y 3 V0, y z 3 V0.
Sx 2 y V0 x2 0 x2y V0 0Sy 2 x V0 y2 0 xy2 V0 0
S 2xy 2yz 2xz 2 xy V0 x V0 y .
a b c k 3.b k 3.a b
Va43 kb 2ab b2
Vb43 ka a2 2ab
0
0
kb 2ab b2
kb a2 2ab
0
0
V 4 abc 3 43 ab k a b 4
3 kab a2b ab2a b c k.
9 pies 9 pies 8.25 pies;x y z 373
f x, y x2y20, 0, 1 .f x, y 1 x y
xy
67
−3
36
z
x
y
2
30
45
60
75
2
z
0, 0, 01, 1, 1x, x, 0 , x 1
2, 1, 9 , 2, 1, 90, 1, 2
±2, 4, 281, 2, 50, 1, 104, 2, 114, 0, 21
0, 3, 1
4 26
xy
2 4 6
z
6
Mínimo absoluto (0, 0, 0)
0, 00, 0, 00, 0
42
6
x
y
−4
−2
4
z
6
Mínimoabsoluto(1, a, 0)
Mínimoabsoluto(b, −4, 0)
1, a , b, 41, a, 0 , b, 4, 01, a , b, 4
x
y
−2
−2
−22
21
z
2
Punto silla(0, 0, 0)
0, 00, 0, 00, 04 < fxy 3, 7 < 4
z
yx3
3
40
60
x y 0.z 0z
1, 1, 10, 0, 040, 40, 3 200
±1, 0, 10, ±1, 41, 0, 2
0, 0, 01, 0, 2
−4
44
−4
56
yx
z
x
y
5
−4
−4
4
4
z
A136 Answers to Odd-Numbered Exercises
y z V0 xy.V0 xyz0
Soluciones_Vol_2.indd 43 3/12/09 20:38:22
A-44 Soluciones de los ejercicios impares
b)
c)
d)e)f ) da la dirección de la máxima tasa de decrecimiento
23. Expresar la ecuación a maximizar o minimizar como una funciónde dos variables. Tomar las derivadas parciales e igualarlas a ceroo indefinido para obtener los puntos críticos. Utilizar el criterio delas segundas derivadas parciales para extremos relativos utilizan-do los puntos críticos. Verificar los puntos frontera.
25. a) b) 27. a) b) 229. 31.
33. a)b) c) 1.6
35.41.4 bushels por acre
37.
39. 41.
43. a)
b)
45. a) b)c) d) Demostración
47. Demostración
Sección 13.10 (página 976)1. 3.
5. 7.9. 11. 13.
15. Máximos:
Mínimos:
17. 19. 21. 23.25. 0.188 27. 29.31. Los problemas de optimización que tienen restricciones sobre los
valores que pueden ser usados para producir las soluciones ópti-mas se conocen como problemas de optimización restringidos.
33. 35.37. $26.73 39.41. Demostración 43.45. pies
47. y 49. Demostración
51.53.
55. a)b)
Los valores máximos ocurren cuando .
3
3
2
3
g 3, 3, 3 18
Costo $55 095.60 y 688.7 x 191.3
P 15 625 18, 3 125 226 869
h 2 3v0
2r 3v0
2
3 360 3 360 43 3 360
2 3a 3 2 3b 3 2 3c 3a b c k 39 pies 9 pies 8.25 pies;
x y z 33
4, 0, 4311 23 22 2f 8, 16, 8 1024
f 2 2, 2 2 12
f 2 2, 2 2 12
f 2 2, 2 2 52
f 2 2, 2 2 52
f 13, 13, 13
13f 3, 3, 3 27f 1, 1 2
f 25, 50 2 600f 1, 2 5f 2, 2 8f 5, 5 25
x
4
44
4
Restricción
y
Curvas de nivel2
2
4
4
6
6
8
8
10
10
12
12
xRestricción
Curvas de nivel
y
2 24
2,000
14,000
P 10,957.7e 0.1499hln P 0.1499h 9.3018
1 14
20
120
y 0.22x2 9.66x 1.79
5
2
7(0, 0)(2, 2)
(3, 6)
(4, 12)
14
2
69( 2, 0)
( 1, 0)
(0, 1)
(1, 2)
(2, 5)
8
y x2 xy 37 x2 6
5 x2635
an
i 1 xi2 b
n
i 1 xi cn
n
i 1 yi
an
i 1 xi3 b
n
i 1 xi2 c
n
i 1 xi
n
i 1 xi yi
an
i 1 xi4 b
n
i 1 xi3 c
n
i 1 xi2
n
i 1 xi2 yi
y 14x 19
050
250
80
y 1.6x 84
4 18
6
(0, 6)
(4, 3)
(5, 0)(8, 4) (10, 5)
y = x +175148
945148
8
2 10
1
7
(0, 0)(1, 1)
(4, 2)
(3, 4)(5, 5)
y x= +37 743 43
y 175148 x 945
148y 3743 x 7
43
y 2x 416y 3
4 x 43
S x, yS x, y
S 7.266x4, y4 0.06, 0.45 ;x2, y2 0.05, 0.90t 1.344;
186.0
12
i 12
210j
y 2x 4 2 y 2 2
Syy
x2 y 2y 2
x 2 2 y 2 2
x 4x 4 2 y 2 2
Sxx
x2 y2x 2
x 2 2 y 2 2
Answers to Odd-Numbered Exercises A137
de S. Usar para encontrar un máximo.
Soluciones_Vol_2.indd 44 3/12/09 20:38:24
A-46 Soluciones de los ejercicios impares
71. 73.75. a) b) 50.6 kg77. Máximo:79.
SP Solución de problemas (página 981)1. a) 12 unidades cuadradas b) Demostración c) Demostración3. a)b)
Entonces el plano tangente es
Intersecciones:
5. a) b)
Valor máximo: Valores máximo y mínimo: 0El método de los multiplicado-res de Lagrange no se aplicaporque
7.
9. a)
b)
11. a)
b)
c)
d)No; la razón de cambio de esmayor cuando el proyectil estámás cerca de la cámara.
e) es máximo cuando segundos.No; el proyectil alcanza su máxima altura cuando
segundos.
13. a) b)
Mínimo: Mínimos:Máximos: Máximos:Puntos silla: Puntos silla:
c)Mínimo: Mínimos:Máximos: Máximos:Puntos silla: Puntos silla:
15. a)
b)
c) Alturad)
17 a 19. Demostraciones
Capítulo 14Sección 14.1 (página 990)
1. 3. 5.7. 9. 11. 3
13. 15. 17. 2 19. 21. 1 629 23. 25. 427. 29. 31. 33. Diverge 35. 2437. 39. 41. 5 43. 45.47. 49.
51. 53.
1
0
y
y f x, y dx dy
ln 10
0
10
ex f x, y dy dx
x− 2 − 1 1 2
2
3
4
y
1
2
4
6
8
2 3
y
x
2
0
4 y2
4 y2 f x, y dx dy
4
0
4
x f x, y dy dx
−2 −1 1 2
−1
3
1
y
x
1 2 3 4
1
2
3
x
y
92ab8
3163
12
2 32 182
23
13
12
83
x2(1 e x2 x2e x2y 2 ln y 2 y24x2 x 4 2y ln 2y2x2
dl 0, dh 0.01: dA 0.06dl 0.01, dh 0: dA 0.01
1 cm
6 cm
1 cm
6 cm±1, 0, e 1
0, 0, 00, ±1, e 10, ±1, e 1±1, 0, e 10, 0, 0
< 0 > 00, 0, 0±1, 0, e 1
0, ±1, 2e 10, ±1, 2e 1±1, 0, e 10, 0, 0
x
y12
−1
1
z
x
y
1
22
z
t 21.41
t 0.98
0 4
−5
30
ddt
16 8 2 t 2 25t 25 264t4 256 2 t3 1024t2 800 2 t 625
arctan 32 2 t 16t2
32 2 t 50 arctan y
x 50
y 32 2t 16t 2x 32 2t
tf x, y tCxay1 a Ctxay1 a
C tx a ty 1 af tx, ty f x, y Cxay1 a Cxay1 a a 1 a axaCy1 a 1 a xaC y1 a
xCy1 aaxa 1 yCxa 1 a y1 a 1x fx y f
y
2 3 150 2 3 150 5 3 150 3
g x0, y0 0.
2 2
y
x32 41−1−2
−3
−2
−4
−1
1
2
k = 2k = 1k = 0
k = 3
g(x, y)
y
x3 411
3
4
1
1
k = 2k = 1k = 0
k = 3
g(x, y)
V 13 bh 9
2
3x0, 0, 0 , 0, 3y0, 0 , 0, 0, 3x0 y0
y01
x0 y0x x0 x0
1x0 y0
y y0 x0 y0 z 1x0 y0
0.
z0 1 x0 y0 x0 y0z0 1y0z0 x x0 x0z0 y y0 x0 y0 z z0 0
z 60 3 2 2 3 6 8.716 kmy 3 3 0.577 km;x 2 2 0.707 km;
f 13, 13, 13
13
y 0.004x2 0.07x 19.4f 49.4, 253 13 201.8x1 94, x2 157
Answers to Odd-Numbered Exercises A139
1053714_ans_14.qxp 10/27/08 3:59 PM Page A139
Soluciones_Vol_2.indd 46 3/12/09 20:38:31