bonjour
3 x + 7 = 7 x + 25
3 x - 7 x = 25 - 7
- 4 x = 18
x = - 18/4 = - 4.5
6 x - 15 = 7 x + 2
6 x - 7 x = 2 + 15
- x = 17
x = - 17
2 x² - 4 x - 6 = 0
si x = - 3
2 ( - 3 )² - 4 * - 3 - 6 = 2 * 9 + 12 - 6 = 18 + 12 - 6 = 24
donc - 3 n'est pas solution
