Réponse :
Explications étape par étape :
exercice 29
a)
7 x + 15 = 6 x + 3
7 x - 6 x= 3 - 15
x = - 12
b)
(-1/3) x + 3 = (2/3) x - 2
3 + 2 = (2/3) x + (-1/3) x
5 = (2/3) x - (1/3) x
5 = (1/3) x
15 = x
c)
3,2 + 8 x = 9 x - 5,1
3,2 + 5,1 = 9 x - 8 x
8,3 = x
d)
0,9 x - 4 = - 0,1 x - 6
0,9 x + 0,1 x = - 6 + 4
x = - 2
exercice 30
a)
12 x + 15 = 6 x + 3
12 x - 6 x = 3 - 15
6 x = - 12
x = - 12/6
x = - 2
b)
5 x - 3 = 2 x + 4
5 x - 2 x = 4 + 3
3 x = 7
x = 7/3
c)
- 7 x - 8 = - 10 x + 4
- 7 x + 10 x = 4 + 8
3 x = 12
x = 12/
x = 4
d)
2 x + 7 = 9 x - 5
7 + 5 = 9 x - 2 x
12 = 7 x
12/7 = x
