Bonsoir,
Soit A= (6x-4)²- (6x-4) (x+3)
1) Développer et réduire A
A= (6x-4)²- (6x-4) (x+3)
A = 36x² - 48x + 16 - (6x² + 18x - 4x - 12)
A = 36x² - 48x + 16 - 6x² - 18x + 4x + 12
A = 36x² - 6x² - 48x - 18x + 4x + 16 + 12
A = 30x² - 62x + 28
2) Factoriser A
A= (6x-4)²- (6x-4) (x+3)
A = (6x - 4) [(6x - 4) - (x + 3)]
A = (6x - 4) (6x - 4 - x - 3)
A = (6x - 4) (5x - 7)
A = 2 (3x - 2) (5x - 7)
3) Calculer A pour x=1
A = 30x² - 62x + 28
A = 30 * 1² - 62 * 1 + 28
A = 30 - 62 + 28
A = - 4.
