Réponse :
Bonjour,
12.
a) 2x + 18 = 4x
2x-4x = -18
-2x = -18
(on multiplie par -1 des deux côtés:)
2x=18
x=18/2 = 9
b) 5x - 10 =4x+ 9
5x - 4x = 9 + 10
x= 19
c) 3x- 12 = -5x - 4
3x + 5x = -4 + 12
8x = 8
x= 8/8= 1
d) x+5 = 4x+4 + 7
x-4x = 4+7-5
-3x = 11-5
-3x =6
x= 6/-3 = -2
e) 3x-7 = -2x + 8
3x+2x = 8+7
5x = 15
x = 15/5 = 3
f) 4x+20 = 10x-30
4x-10x = -30-20
-6x = -50
x= 50/6
