* |2x+7| = 15 + |-27| - (13 - 17 + |-20| ) - |-2x-7|
<=> |2x + 7| = 15 + 27 - ( 13 - 17 + 20) - |- (2x + 7)|
<=> |2x + 7| = 26 - |2x + 7|
<=> |2x + 7| + |2x + 7| = 26
<=> 2 . |2x + 7| = 26
<=> |2x + 7 | = 13
<=> 2x + 7 = 13 hoặc 2x + 7 = -13
<=> 2x = 6 hoặc 2x = -20
<=> x = 3 hoặc x = -10
* -5 . |x + 4| = 21 : (-3) + 2 . |-x - 4|
<=> - 5 . | x + 4| = -7 + 2 . | - (x + 4)|
<=> - 5 . | x + 4 | = - 7 + 2 . | x + 4|
<=> 2 . | x + 4 | + 5 . |x + 4| = 7
<=> 7 . |x + 4| = 7
<=> | x + 4 | = 1
<=> x + 4 = 1 hoặc x + 4 = -1
<=> x = -3 hoặc x = -5
* -7 . |3x - 1| = -16 . 2 - 32 : (-4) + | 1 - 3x |
<=> -7 . |3x - 1| = -8 + 8 + | - (3x - 1)|
<=> - 7 . |3x - 1| = | 3x - 1 |
<=> |3x - 1| + 7 . |3x - 1| = 0
<=> 8 . |3x - 1| = 0
<=> |3x - 1| = 0
<=> 3x - 1 =0
<=> 3x = 1
<=> x =1/3
