III. PHAN PHOI THC)I LUONG Bai nay day trong 1 tiet:
a)Nhi thurc bae nhat
• GV neu khai niem ve nhi thiic bae nhat.
Nhi thiic bdc nhdt ddi vdi x Id bieu thitc dqngf(x) = ax + b trong
Sau do dua ra cac cau hdi sau, nhim khic sau dinh nghia. HI. Hay neu mot vi du ve nhi thiic bae nhat cd a < 0. H2. Hay neu mdt vi du ve nhi thiic bae nhat cd a > 0. H3. Hay xac dinh nghiem ciia nhi thiic/(x) = ax + i». b) Dau cua nhi thiic bae nhat
• GV neu dinh li:
Nhi thitc bdc nhdt f(x) = ax + b ciing ddu vdi he sd a khi x Idn han nghiem, vd trdi ddu vdi he sda khi x nhd haii nghiem ciia nd.
af(x) > 0 <:^ X > XQ.
af(x) < 0 <=> X < XQ.
Kit qua tren dugc tdm tdt trong bdng sau :
X
f(x) = ax + b
- c o XQ +00
trai da'u vdi a 0 ciing da'u vdi a
Sau do GV neu mdt vi du (nen la'y khac SGK). + Xet bieu thiic f(x) = - 3x + 5 :
Hay dien nghiem va da'u ciia /(x) vao bang sau:
x f(x) = -3x + 5
- 0 0 X o = . . . +00
0
+ Xet bieu thiic f(x) = 2x - 5 :
Hay dien nghiem va dau cua f(x) vao bang sau:
f(x) = 2x - 5
- 0 0 X n = . + 0 0
0
Thuc hien H1
GV: thuc hien thao tdc ndy trong Sphiit.
Hoat ddng cua GV Cau hdi 1
Vdi a > 0, tung do cua nhirng diem ma hoanh do Idn hon XQ cd da'u nhu the' nao?
Cau hdi 2
Vdi a > 0, tung do cua nhiing diem ma hoanh do nhd hon XQ cd da'u nhu the' nao?
Cau hdi 3
Hay xet tirang tu vdi a < 0.
Hoat ddng cua HS Ggi y tra Idi cau hdi 1 (adsbygoogle = window.adsbygoogle || []).push({});
Dau duong
Ggi y tra Idi cau hdi 2