Réponse:
Bonjour,
3x+7 = 0
3x = -7
x = -7/3
6-x = 4
-x = 4-6
-x = -2
x = 2
3(x+7) = x+1
3x+21 = x+1
3x-x = 1-21
2x = -20
x = -20/2
x = -10
3x+7 = x-1
3x-x = -1-7
2x = -8
x = -8/2
x = -4
6-x = x+14
-x-x = 14-6
-2x = 8
x = -8/2
x = -4
3(x+7) = 4x+9
3x+21 = 4x+9
3x-4x = 9-21
-x = -12
x = 12