Sagot :
Bonjour
G = (x-5)² - (x-5)(7 - 2x)
G = x² -10x+25 - ( 7x -2x² -35 +10x)
G = x² -10x +25 -7x +2x² +35 -10x
G = 3x² -27 x +60
G = (x-5)(x-5) - (7-2x)
G = (x-5)(x-5-7+2x)
G = (x-5)(3x -12)
Pour x = -3
G = (-8)(-9-12) = -8 x -21 = 168
(x-5)(3x-12) = 0
soit x-5 = 0 alors x = 5
soit 3x-12 = 0 donc 3x = 12 et x = 4
G = (x-5)^2 - (x-5)(7-2x)
G = x^2 - 5^2 - 7x + 2x^2 + 35 + 10x
G = 3x^2 + 3x + 10
PS : ^2 est le signe "au carré"