Bonjour,
Il faut savoir : a*b + a*c = a*(b+c). Soit x dans R. On a :
D = (4x+7)[ (2x-5) - (5x+2) ] = (4x+7)*(-3x-7) = -(4x+7)*(3x7)
E = (3x+2)(x-1) - (x-1)² = (x-1)*[ (3x+2) - (x-1) ] = (x-1)*(2x+3)
F = (5x-4)² - (x-7)*(5x-4) = (5x-4)* [ (5x-4) - (x-7) ] = (5x-4)*(4x+3)
