a) 2x + 5 = x - 7
2x -x = -7 - 5
x = -12
b) | x | = | 8 |
| x | = 8
=> x = 8
hoặc x = -8
c) | 2x-1 | = | -13 |
| 2x-1 | = 13
=> 2x-1 = 13
2x = 13 + 1
2x = 14
x = 14:2
x = 7
hoặc 2x-1 = -13
2x = -13 + 1
2x = -12
x = -12 : 2
x = -6
d) 5x + 4 = 3x - 6
5x - 3x = - 6 - 4
2x = -10
x = -10 : 2
x = -5
n) ( 5x - 10 ) ( 6x + 1 ) = 0
ta chia 2 TH
TH1 5x- 10= 0
5x = 0+10
5x = 10
x = 10:5
x = 2
TH2 6x +1 =0
6x = 0+ 1
6x = 1
x = 1: 6
x =\(\varnothing\)
vậy x =2