原式=x（x+1）（x-1）（x+2）-24 =x（x2-1）（x+2）-24 =x（x3+2x2-x-2）-24 =x4+2x3-x2-2x-24 =（x4-2x3）+4x3-x2-2x-24 =x3（x-2）+4x3-8x2+7x2-2x-24 =（x3+4x2）（x-2）+（7x2-14x）+（12x-24）=（x3+4x2+7x+12...