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}