Réponse :
Explications étape par étape
Bonsoir
D = (7x + 4)(6x + 8) - (4x + 5)(7x + 4)
a) calculer pour x = -2 :
D = (7 * (-2) + 4)(6 * (-2) + 8) - (4 * (-2) + 5)(7 * (-2) + 4)
D = (-14 + 4)(-12 + 8) - (-8 + 5)(-14 + 4)
D = (-10) * (-4) - (-3) * (-10)
D = 40 - 30
D = 10
b) developper D :
D = (7x + 4)(6x + 8) - (4x + 5)(7x + 4)
D = 42x^2 + 56x + 24x + 32 - (28x^2 + 16x + 35x + 20)
D = 42x^2 - 28x^2 + 80x - 51x + 32 - 20
D = 14x^2 + 29x + 12
c) recalculer pour x = -2 :
D = 14 * (-2)^2 + 29 * (-2) + 12
D = 14 * 4 - 58 + 12
D = 56 - 46
D = 10
d) factoriser :
D = (7x + 4)(6x + 8) - (4x + 5)(7x + 4)
D = (7x + 4)(6x + 8 - 4x - 5)
D = (7x + 4)(2x + 3)
e) Recalculer pour x = -2 :
D = (7 * (-2) + 4)(2 * (-2) + 3)
D = (-14 + 4)(-4 + 3)
D = -10 * (-1)
D = 10
f) developper l’expression trouvé au d) :
D = (7x + 4)(2x + 3)
D = 14x^2 + 21x + 8x + 12
D = 14x^2 + 29x + 12
