Réponse :
Bonjour,
1) C = (3x – 2)²+ (3x – 2)(x + 3)
= 9x² - 12x + 4 + 3x² + 9x – 2x – 6
= 9x² + 3x² – 12x + 9x – 2x + 4 – 6
= 12x² – 5x – 2
2) C = (3x – 2)²+ (3x – 2)(x + 3)
= (3x – 2)(3x – 2) + (3x – 2)(x + 3)
= (3x – 2)[(3x – 2) + (x + 3)]
= (3x – 2)(3x – 2 + x + 3)
= (3x – 2)(4x + 1)
3) (3x – 2)(4x + 1) = 0
Or A × B = 0 ⇔ A = 0 ou B = 0
3x – 2 = 0
3x = 2
x = 2/3
ou
4x + 1 = 0
4x = -1
x = -1/4
Donc S = {-1/4 ; 2/3}
