Réponse :
bonjour
Explications étape par étape :
1) g(x) = (3x + 15)² - 36
= ((3x)² + 2×3x×15 + 15²) - 36
= 9x² + 90x + 225 - 36
= 9x² + 90x +189
2) g(x) = (3x+15-6)(3x+15+6)
= (3x+9)(3x+21)
= 3(x+3)3(x+7)
= 3×3(x+3)(x+7)
= 9(x+3)(x+7)
3) a. 9x² + 90x +189 = 189
9x² +90x = 0
-b/a = -90/9 = -10 et 0
b. (3x+15)² - 36 = -36
(3x+15)² = 0
9x² +90x +225 = 0
x² +10x +25 = 0
(x+5)² = 0
x+5 = 0
x = -5
