bonjour,
8 x + 3 = 0
8 x = - 3
x = - 3/8
2 x - 9 = 0
2 x = 9
x = 9/2
49 - 7 x = 0
- 7 x = - 49
x = 7
- 6 x - 5 = 0
- 6 x = 5
x = - 5/6
10 x + 1 = - 7
10 x = - 7 - 1
10 x = - 8
x = - 8/10 = - 4/5
9 x - 2 = 6
9 x = 6 + 2
9 x = 8
x = 8/9
20 - 4 x = - 4
- 4 x = - 4 - 20
- 4 x = - 24
x = 6