a) (5x+2)² - (5x+2)(x-5) = 25x² + 20x + 4 - (5x²-25x+2x-10)
= 25x² + 20x + 4 - 5x² + 23x + 10
= 20x² + 43x + 14
b) le facteur commun est (5x+2) :
<=> (5x+2) (5x+2 - (x-5))
<=> (5x+2) (4x+7)
c)
f(0) = (5(0) + 2) (4(0) + 7) = 2*7 = 14
f(-2) = (5*(-2) + 2) (4*(-2) + 7) = (-10 + 2) (-8 + 7)
= -8 * -1 = 8
Résoudre f(x) = G ??? genre pour G = 0 ?
f(x) = G = 0
(5x+2) (4x+7) = 0
equation produit nul :
5x + 2 = 0 ou 4x + 7 = 0
x = -2/5 ou x = -7/4
Bonne soirée.
