Réponse :
Explications étape par étape :
Bonjour
A = 8x - 12 et b = (x + 4)(2x - 6)
1) x = 3
A = 8 (3) - 12 = 24 - 12 = 12
x = - 1
A 8 (-1) - 12 = - 8 - 12 = - 20
2)
A = 0 ⇒ 8x - 12 = 0 ⇒8x = 12⇒x = 12/8 = (3×4)/(2×4) = 3/2
A = 0 pour x = 3/2
S = {3/2}
3)
x = 3
B = (3+ 4 ) (2(3) -6) = 7 × (6 - 6) = 7×0 = 0
x = - 1
B = ((-1) + 4)(2 (-1) - 6) = (- 1 + 4)(-2 - 6)= 3 × (-8) = -24
4)
B = 0 ⇒ (x + 4) (2x - 6) = 0
soit x + 4 = 0 ou 2x - 6 = 0
soit x = -4 ou 2x = 6
soit x = - 4 ou x = 6/2
soit x = - 4 ou x = 3
S ={ - 4; 3}
5) A = 8x - 12 = 4 × 2x - 4 ×3 = 4 (2x -3)
6) B = (x + 4) (2x - 6) = 2x² - 6x + 8x - 24 = 2x² + 2x - 24
B = 2x² + 2x - 24
