III. CHUA BAI TAP ON TAP CHUONG IV Bai 76.
Vx^ +i V?+i H2 Hay ap dung bat ding thiic Cd-si cho hai sd tren.
H2. Hay ap dung bat ding thiic Cd-si cho hai sd tren.
Bai 79.
Hoat ddng ciia GV Hoat ddng cua HS Cau hdi 1
Hay giai bat phuang trinh: 7 1 3 13
— X — > — X
6 2 2 3
Cau hdi 2
Giai bat phuang trinh
m x + 1 >m -x
Ggi y tra Idi cau hdi 1
Bat phuang trinh da cho tuong duong vdi:
7 x - 3 > 9 x - 2 6 hay 2 x - 2 3 < 0 Vay
23 x < — x < —
2
Ggi y tra Idi cau hdi 2
Bat phuang trinh da cho tuong duang
2 4 vdi (m +l)x>m - 1 hay vdi (m +l)x>m - 1 hay x > 4 1 m - 1 m^ +1 m^-l Cau hdi 3
De he cd nghiem cin didu kien gi?
Ggi y tra Idi cau hdi 3
2 1 23
w - 1 < —
Bai 80.
Hoat ddng cua GV Cau hdi 1
Hay dua bat phuang trinh vd
dang ax + b>0
Cau hdi 2
Tim nghiem cua bat phuang trinh.
Cau hdi 3
Bat phuang trinh da cho nghiem diing vdi mgi x e [ - 1 ; 2] khi nao?
Hoat ddng cua HS Ggi y tra Idi cau hdi 1
Bat phuang trinh da cho tuong duong vdi:
(m^ +m + \)x + 3m + \>0
Ggi y tra Idi cau hdi 2
Bat phuang trinh da cho cd nghiem la - 3 w - l
^ - 2
m +m + \
Ggi y tra Idi cau hdi 3
^^, . - 3 m - 1 , , ^ Khi -^ > -1 hay 0 < m < 2. m +OT + 1 Bai 81. GV chiia cau a) 'Hoat ddng cua GV Cau hdi 1 Hay Tinh A. Cau hdi 2
Hay bien luan bat phuang trinh da cho.
Hoat ddng cua HS Ggi y tra Idi cau hdi 1
A= -l(m-\)(m + l)
Ggi y tra Idi cau hdi 2
Ne'u A < 0 <=> m < -7 hoac m > 1, bat phuang trinh nghiem diing vdi moi
X G M.
Neu -7 < m < 1 <z> A > 0 ba't phuong trinh cd tap nghiem la mdt khoang. GV tu vie't khoang nghiem.
a) Hudng ddn.
Bat phuang trinh cd dang: (a^ -3a + 2)>2
Tit dd dua ra each bien luan bat phuang trinh.
Bai 82.
GV chiia cau b)
Hoat ddng cua GV Cau hdi 1
Hay dua bat phuang trinh ve dang: '^^''^>0.
• Qix)
Cau hdi 2
Hay lap bang xet da'u va vie't tap nghiem cua bat phuang trinh.
Hoat ddng cua HS Ggi y tra Idi cau hdi 1
Bat phuong trinh cd dang:
x ^ - 3 x + 2
Ggi y tra Idi cau hdi 2
Tap nghiem ciia bat phuang trinh: ( - o ) ; l ) u ( 2 ; 3 ] L J [ 4 ; + a)).
a) Hudng ddn.
Lap bang xet dau va dua ra tap nghiem.
S = i2;4)Kj(5; + cc).
Bai 83.
GV chiia cau a)
Hoat ddng ciia GV Cau hdi 1
Hay viet bat phuang trinh khi m = 4.
Cau hdi 2
Hay neu dieu kien de bat phuang trinh cd nghiem vdi mgi X G R.
Hoat ddng cua HS Ggi y tra Idi cau hdi 1
Khi m= 4, bat phuang trinh cd dang: 2m - 1 < 0. Bat phuong trinh khdng cd nghiem vdi moi x G R.
Ggi y tra Idi cau hdi 2
fA<0 Dieu kien la <
, , . , . ^ 12-2V3 khi do m <
3
b) Hudng ddn.
Lap luan tuong tu cau a). m < - l hoac m > 2.
Bai 84.
Hudng ddn. HS xem lai cac bai tap cua bai 8.
GV hudng din HS thuc hien theo cac cau hdi sau: a) HI. Cd the giai phuang trinh theo nhirng each nao? H2. Neu binh phuang hai ve' can dieu kien gi?
Ddp sd. X = ± 1 va X = 5.
b) a) HI. Cd the giai phuong trinh theo nhirng each nao? H2. Ne'u binh phuong hai ve' can dieu kien gi?