soluzione Scomporre     (4x - 4y)(2x + 3y) - (x - y)2 - 4x2 + 4y2 = = 4(x - y)(2x + 3y) - (x - y)2 - 4(x - y)(x + y) = = (x - y)[4(2x + 3y) - (x - y) - 4(x + y)] = = (x - y)[8x + 12y - x + y - 4x - 4y] = =(x - y)(3x + 9y) = = 3 (x - y)(x + 3y)