Bonjour !
a. 9x + 15
= 3 * 3x + 3 * 5
= 3(3x + 5)
b. 5x² - 15x
= 5 * x² - 5 * 3x
= 5(x² - 3x)
c. (x + 5)(x + 1) - 4x(x + 1)
= (x + 1)[(x + 5) - 4x]
= (x + 1)(x + 5 - 4x)
= (x + 1)(-3x + 5)
d. (5x + 3)² + 5(4x - 2)(5x + 3)
= (5x + 3)[(5x + 3) + 5(4x - 2)]
= (5x + 3)(5x + 3 + 20x - 10)
= (5x + 3)(25x - 7)
e. (3x + 3) + 4x(x + 1)
= 3(x + 1) + 4x(x + 1)
= (x + 1)(3 + 4x)
f. (2x + 1)² + (8x + 4)
= (2x + 1)(2x + 1) + 4(2x + 1)
= (2x + 1)(2x + 1 + 4)
= (2x + 1)(2x + 5)
J'espère t'avoir aidé. Bon courage !
