x + x + x + 91 = -2
x + x + x = -2 - 91
x + x + x = -93
3x = -93
x = -93 : 3
x = -31
-152 - (3x + 1) = (-2) . (-27)
-152 - (3x + 1) = 54
3x + 1 = -152 - 54
3x + 1 = -206
3x = -206 - 1
3x = -207
x = -207 : 3
x = -69
|5x + 1| = 11
5x + 1 = 11 hay 5x + 1 = -11
5x = 11 - 1 hay 5x = -11 - 1
5x = 10 hay 5x = -12
x = 10 : 5 hay x = -12 : 5
x = 2 hay x = -2,4
Mà x ∈ Z
x = 2