soluzione Scomporre     (x - 2)3 - (x + 1)3 = = [(x-2)-(x+1)] [(x - 2)2 + (x - 2)(x+1) + (x+1)2]= = (x-2-x-1) (x2 -4x + 4 + x2 - 2x + x - 2 + x2 + 2x + 1) = = (-3) (3x2 -3x + 3)= = (-9) (x2 -x + 1)