bonsoir
L = ( 2 x - 3) ( - x + 4) - ( 4 x - 6) ( 2 x - 1) + ( 3 x + 8)
L = ( - 2 x² + 8 x + 3 x - 12) - ( 8 x² - 4 x - 12 x + 6) + 3 x + 8
L = - 2 x² + 11 x - 12 - 8 x² + 16 x - 6 + 3 x + 8
l = - 10 x² + 30 x - 10
pour x = - 3
l = - 10 ( -3)² + 30 ( -3) - 10
l = - 90 - 90 - 10
l = - 190
- 4 x + 10 = - 2 x - 6
- 4 x + 2 x = - 6 - 10
- 2 x = - 16
x = 8