-2 est la solution de l'équitation : A = -5x+4=14     B = 5x-4=14     C = -5x-4=-14

A
-5x+4 = 14
-5x = 14-4
-5x = 10
x = -10/5
x = -2

B
5x-4 = 14
5x = 14+4
5x = 18
x = 18/5

C
-5x-4 = -14
-5x = -14+4
-5x = -10
x = -10/-5
x = 2

-2 est solution de l'équation A