III. PHAN PHOI THC)I LUONG Bai nay day trong 2 tiet:
7x-i > o [2x + l>
(a) He bat phuang trinh tren cd nghiem la x > —
(b) He bat phuong trinh tren cd nghiem la x > 0 (c) He bat phuang trinh tren cd nghiem la x > 1 (d) He bit phuong trinh tren vd nghiem.
Hay chgn ket qua diing.
Trd Idi. Chgn (c)
8. Cho he bat phuang trinh
-7x + 7>0 2x +1 > 0 2x +1 > 0
(a) He ba't phuang trinh tren cd nghiem la x > - 1
(b) He bat phuang trinh tren cd nghiem la x < 49
(c) He bat phuong trinh tren cd nghiem la 0 < x < 49
(d) He ba't phuang trinh tren cd nghiem — < x < 49.
Hay chgn ket qua diing.
Trd Idi. Chgn (c)
9. Cho he bat phuang trinh
- 7 x + 7>0
27^7^ + l>0 (a) He bat phuong trinh tren cd nghiem la x > - 1 (a) He bat phuong trinh tren cd nghiem la x > - 1
(b) He bit phuang trinh tren cd nghiem la x < 49 60
(c) He bat phuang trinh tren cd nghiem la 1 < x < 49 (d) He bat phuang trinh tren cd nghiem 0 < x < 49. Hay chgn ket qua diing.
Trd Idi. Chgn (c)
HUdNG DAN B A I TAP SGK
Bai 25.
De gidi cdc bdi tap ndy HS edn ndm dugc: - Cdch gidi bdt phuang trinh bdc nhdt. - Bie'n ddi tuang duang cdc bdt phang trinh.
Hudng ddn. 4 a ) x < - - b ) x < - 5 . c) De y 3 - 272 = 1 - 272 + 2 = (1 - 72)^ va 1 - 72 < 0 , cd(l - 72)x < 3 - 272 <» (1 - 72)x < (1 - 72)^ o x > 1 - 72. d) (x + 73)2 > ^^ _ ^ ^ 2 + 2 <:^ (x + 73)2 _ (^ _ ^ ) 2 > 2 <^ 473x > 2 <^ X > ^ 6 Bai 26.
De gidi cdc bdi tap ndy HS edn ndm dugc: - Cdch gidi bdt phuang trinh bdc nhdt.
- Gidi vd bien luan bdt phuang trinh bdc nhdt. - Bie'n ddi tuang duang cdc bdt phuang trinh. Hudng ddn cdu a)
ta
Hay bien ddi bat phuang trinh ve dang / ( x ) > 0.
Cau hdi 2
Hay giii va bien luan bat phuang trinh tren.
( m - l ) x - ( w 2 - l ) < 0
Ggi y tra Idi cau hdi 2
- Neu m = 1 thi T = R ;
- Ne'u m > 1 thi T = (-oo ; m + 1] ;
- Neu m < 1 thi T = [m + 1 ; +<x>).
Tra Idi cac cau con lai
b) Neu m = 2 thi T = 0 ; neu m > 2 thi T = (3 ; +oo); ne'u m < 2 thi T = (-« ; 3).
c) Neu k = 2 thi T = R ; neu k > 2 thi T =
T = f 4 - k ^ ; + 00 U - 2 ' J ( 4 - k ^ - 0 0 ; — • — I k - 2 j ; neu k < 2 thi d) (a + l)x + a + 3 > 4x + 1 c^ (a - 3)x > - a - 2. Vay - Neu a = 3 thi T = R ; - Neu a > 3 thi T = - Neu a < 3 thi T = ' 2 + a ; + 00 _ 3 - a ( 2 + a" - 0 0 ; I 3 - a J J Bai 27.
Degidi cdc bdi tap ndy HS edn ndm dugc: - Cdch gidi he bdt phuang trinh bdc nhdt. - Bie'n ddi tuang duang cdc bdt phuang trinh. Hudng ddn cdu a)
Hoat ddng ciia GV Cau hdi 1
Hay giai bat phuang trinh
Hoat ddng cua HS Ggi y tra Idi cau hdi 1
5 x - 2 >4x + 5
Cau hdi 2
Hay giai bat phuang trinh 5 x - 4 > x + 2.
Cau hdi 3
Hay giai he bat phuong trinh f5x - 2 > 4x + 5
(5x - 4 < X + 2
Tra Idi cac cau con lai
f2x + 1 > 3x + 4 fx b) <^
[5x + 3 > 8x - 9 [3
Ti = (7 ; + 00).
Ggi y tra Idi cau hdi 2
Ti = (- ex. ; 2).
Ggi y tra 161 cau hdi 3
T = T, n T 2 = 0 .
< - 3
<:^ X < - 3 . X < 12