Tun: 13 Tit: 40 Ngy dy:14/11/14

Chng II: S NGUYN 1. LM QUEN VI S NGUYN M TP HP CC S NGUYN

I. MC TIU:

* Kin thc: Bit c nhu cu cn phi m rng tp N. Bit c tp hp s nguyn, im biu din s nguyn a trn trc s, s i ca s nguyn.

* K nng: Nhn bit v c ng cc s nguyn m qua v d thc tin. Bit cch biu din cc s t nhin v cc s nguyn m trn trc s. Bc u c th hiu c rng c th dng cc s nguyn ni v cc i lng c hai hng ngc nhau.

* Thi : Yu thch mn hc. Bc u c thc lin h bi hc vi thc tin. II. CHUN B:

- HS: Xem trc bi, thc k c chia n v. - GV: Nhit k c chia m, hnh v biu din cao (m, dng, 0)

Thc k c chia n v. III. TIN TRNH BI DY: 1. n nh 2. Kim tra 3.Tin hnh bi mi

GV gii thiu s lc v chng S nguyn. (4 pht) GV yu cu HS thc hin cc php tnh: 4 + 6; 4 .6; 4 - 6 GV gii thiu nhu cu phi c mt loi s mi. l ni dung ca chng ny.

Hot ng ca thy Hot ng ca tr Kin thc

GV: Trong mi gia nh thng c mt thit b quen thuc l nhit k dng o nhit . GV: Chiu Slide nhit k GV: Trong thc t bn cnh cc s t nhin ngi ta cn dng cc s t nhin c du tr pha trc (nh ta quan st). Cc s c gi l s nguyn m GV: Gii thiu cch c v cch vit s nguyn m. GV: Thc t s nguyn m dng trong cc lnh vc g? Chng ta cng nghin cu cc v d sau. I. Lm quen vi s nguyn m 1. Cc v d GV: Gii thiu cc v d tng t sgk. (Chiu Slide) v d 1 GV: - Nhit ca nc ang tan l 00C - Nhit nc ang si l 1000C - Nhit trong ngn lnh ca t lnh l di 00C

- Tr li theo s hiu bit vn c. -Nghe ging. - c phn v d 1 (sgk: tr 66) v thc hin ?1 .

I. Lm quen vi s nguyn m 1. Cc v d: a) V d 1 Nhit 3 di 00C vit l 30C (v c l m ba C hoc tr ba C).

V d nhit 3 di 00C vit l 30C (v c l m ba C hoc tr ba C). + hiu hn v nhit m ta cng lm ?1 trong SGK/66 Nh vy s nguyn m trong v d trn ch nhit di 00C, vy s nguyn m cn dng trong lnh vc g? Ta cng sang v d 2 + Chiu Slide o cao thp cc a im khc nhau trn Tri t ngi ta ly mc nc bin lm chun. + Quy c mc nc bin l 0m + Khi cao nguyn c Lc c cao trung bnh trn mc nc bin l 600m. Ta ni cao trung bnh ca ca cao nguyn c Lc l 600m + Thm lc a Vit Nam c cao trung bnh thp hn mc nc bin l 65m. Ta ni cao trung bnh ca thm lc a Vit Nam l -65m + hiu hn v cao ca cc im khc nhau ta cng thc hin ?2 Nh vy s nguyn m trong v d trn ch cao di mc nc bin, vy s nguyn m cn dng trong lnh vc g? Ta cng sang v d 3 + Nu ng A c 10000 ta ni ng A c 10000 + Nu ng A n 10000 ta ni ng A c -10000 + hiu hn iu ny chng ta cng thc hin ?3 GV: Khng nh li ngha ca s nguyn m trong thc t thng c s dng trong trng hp no ? + Chiu Slide nhit k + Chng ta quan st nhit k trn hnh v. Nu cc s ca nhit k biu din trn mt ng thng th cc s ny nm trn trc s m ta s c hc ngay sau y. 2. Trc s GV: Gii thiu trc s nh sgk.

-Nhit 3 di 00C. - Hot ng tng t v d 1. ?2- cao ca nh ni Phan - xi- png l 3 143 mt. - cao ca y vnh Cam Ranh l m 30 mt, hay tr 30 mt. - Tng t vi ?3.

b) V d 2: + cao trung bnh ca thm lc a Vit Nam l -65m

c) V d 3:

+ Nu ng A n 10000 ta ni

ng A c -10000

2. Trc s:

GV: Gi HS xc nh cc yu

t ca trc s gm (gc, chiu,

n v).

GV: Cho hc sinh thc hin bi tp ?4 SGK. GV: Gii thiu phn ch cch

v trc s theo cch khc

GV: Trong thc t ta c th v trc s thng ng nh hnh 34 SGK. + Chiu Slide trc s thng ng GV : Cc em quan st trc s ta thy. Cc s 0 ;1 ;2 ;3 ;4 ......l tp hp cc s t nhin N m ta c hc, kt hp vi cc s -1 ;-2 ;-3..... l cc s nguyn m ta va c hc trn lm thnh tp s mi c tn gi l tp s nguyn. Chng ta chuyn sang *) Hot ng nhm: Bi tp da trn bi 4/68 SGK

HS: Lm ? 4.

- Da vo H. 33 *) Hot ng nhm: Bi tp da trn bi 4/68 SGK

-3 -2 -1 43210

Chiu m Gc Chiu dng - im 0 c gi l im gc ca trc s. - Chiu t tri sang phi gi l chiu dng. - Chiu t phi sang tri gi l chiu m. *) Hot ng nhm: Bi tp da trn bi 4/68 SGK

II. Tp hp cc s nguyn 1. s nguyn - Gii thiu tn cc loi s: + S nguyn m v tp hp s nguyn m. + S nguyn dng v tp hp cc s nguyn dng. + Tp hp cc s nguyn v k hiu. *) ch : +) s 0 khng l s nguyn m v cng khng l s nguyn dng. +) im biu din s nguyn a trn trc s gi l im a. ? Tp hp N quan h nh th no vi tp Z. + Trong thc t i sng s nguyn thng c dng khi no? + Chiu Slide Vy ton hc c bt ngun t thc t cuc sng v ton hc cng l mn hc phc v i sng con ngi. - Quan st trc s. - Cc s -1 v 1 cch 0 my n v?

- Xc nh trn trc s: - S t nhin. - S nguyn m . - Quan st trc s v nghe ging . - Tp hp N l con ca tp Z . - Nu nhn xt sgk v v d minh ho cch s dng s nguyn m, nguyn dng . - Quan st v nghe ging .

II. Tp hp cc s nguyn 1. S nguyn: Tp hp ...; 3; 2; 1;0;1;2;3;... gm: +) Cc s nguyn m: ...; 3; 2; 1 +) Cc s nguyn dng:

1;2;3;... +) S 0 khng l s nguyn dng v cng khng l s nguyn m. * Ch : Sgk : tr 69.

V hai s 1 v -1 c gi l 2 s i nhau. 2. S i: ? Tm v d trn trc s nhng cp s cch u im 0 ? - Khng nh l cc s i nhau . ? Hai s i nhau khc nhau nh th no. - Hng dn tng t vi ?4 - Ch : s i ca 0 l 0

- Quan st trc s v tr li cc cu hi . - V d : 1 v -1 ; 2 v -2 ; 3 v -3 .. - Khc nhau v du + ,-. - Thc hin tng t v d .

2. S i: +) 1 v -1 l hai s i nhau. 1 l s i ca s -1, ngc li -1 l s i ca s 1 +) S i ca s 0 l 0 . Vd : 1 l s i ca -1 ; -2 l s i ca 2

III. Cng c +) Chiu Slide +) Tr chi

Hs pht biu Hc sinh cng chi

III. Cng c

4. Hng dn hc nh:

- Xem li kin thc hc - n tp li cch c cc s nguyn - Lm BT 3, 5 SGK/68 - Lm bi tp 8/70 v 10/71 sgk - Xem trc 3 Th t trong tp hp cc s nguyn

5. Rt kinh nghim: ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

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