a) déjà factorisé
c)
f(x)=2(x-3)(x+7)-(2x+1)(x+7)
f(x)=(2x-6)(x+7)-(2x+1)(x+7)
f(x)=(x+7)(2x-6-2x-1)
f(x)=-7(x+7)
e)
f(x)=(x-2)(x+1)-(x²-4)
f(x)=(x-2)(x+1)-(x²-2²)
f(x)=(x-2)(x+1)-(x-2)(x+2)
f(x)=(x-2)(x+1-(x+2)
f(x)=(x-2)(x+1-x-2)
f(x)=(x-2)(-1)
f(x)=-x+2
g)
f(x)=x(3x-5)-(3x-5)
f(x)=(3x-5)(x-1)