Factoriser C : C = (x+13)(x+1)-4(x+1)²
on factorise par x+1
c = (x+1)[(x+13)-4(x+1)]
c = (x+1)(x+13-4x-4)
c = (x+1)(-3x+9)
on factorise par 3
c = 3(x+1)(-x+3)
