Répondre :
f(x) = x²-9-2(x-3)-(3x-1)(3x-9).
=(x-3)(x+3)-2(x-3)-3(3x-1)(x-3)
=(x-3)(x+3-2-9x+3)
=(x-3)(-8x+4)
=4(x-3)(1-2x)
=(x-3)(x+3)-2(x-3)-3(3x-1)(x-3)
=(x-3)(x+3-2-9x+3)
=(x-3)(-8x+4)
=4(x-3)(1-2x)