Réponse :
factoriser
A = 15 x² + 20 x = 5 x(3 x + 4)
B = 6 x - 15 x² = 3 x(2 - 5 x)
C = 5 x(x + 1) + 3(x + 1) = (x + 1)(5 x + 3)
D = (3 x + 5)(x - 1) + 3(x - 1) = (x - 1)(3 x + 5 + 3) = (x - 1)(3 x + 8)
E = (3 x + 5)(x - 1) + (5 x - 7)(x - 1) = (x - 1)(3 x + 5 + 5 x - 7) = (x - 1)(8 x - 2)
= 2(x - 1)(4 x - 1)
F = (3 x + 5)(x - 1) - (5 x - 7)(x - 1) = (x - 1)(3 x + 5 - 5 x + 7) = (x - 1)(12 - 2 x)
= 2(x - 1)(6 - x)
G = (7 x - 3)² - 5(7 x - 3) = (7 x - 3)(7 x - 3 - 5) = (7 x - 3)(7 x - 8)
H = (5 x - 2)(2 x + 7) - (5 x - 2) = (5 x - 2)(2 x + 7 - 1) = (5 x - 2)(2 x + 6)
= 2(5 x - 2)(x + 3)
Explications étape par étape :
il faut voir le facteur commun
C = 5 x(x + 1) + 3(x + 1) le facteur commun est (x + 1)
= (x + 1)(5 x + 3)
