(x²-3x）²-2（x²-3x）-8
=(x²-3x-4)(x²-3x+2)
=(x-4)(x+1)(x-1)(x-2)(x²-3x-4)(x²-3x+2)中的-4是怎么的来的(x²-3x）²-2（x²-3x）-8=(x²-3x）²+(-4+2)（x²-3x）+(-4)×2=(x²-3x-4)(x²-3x+2)