Bonjour,
On donne A = (2x + 4)² - (2x + 4)(5x + 3)
a) Développer et réduire A.
A = (2x + 4)² - (2x + 4)(5x + 3)
A = 4x² + 16x + 16 - (10x² + 6x + 20x + 12)
A = 4x² + 16x + 16 - 10x² - 6x - 20x - 12
A = 4x² - 10x² + 16x - 6x - 20x + 16 - 12
A = - 6x² - 10x + 4
b) Factoriser A.
A = (2x + 4)² - (2x + 4)(5x + 3)
A = (2x + 4) [(2x + 4) - (5x + 3)]
A = (2x + 4) (2x + 4 - 5x - 3)
A = (2x + 4) (- 3x + 1)
A = 2 (x + 2) (-3x + 1)
c) Calculer A pour x =-3.
A = - 6x² - 10x + 4
A = - 6 * - 3² - 10 * - 3 + 4
A = - 6 * 9 + 30 + 4
A = - 54 + 34
A = - 20.