(a-b)²(x-y)-(b-a)(y-x)²
=(a-b)(x-y)（a-b+(x-y)）
=(a-b)(x-y)×（ a-b+x-y）mn²(x-y)的三次方+m²n(x-y)的四次方，分解后的结果等于mn²(x-y)的三次方+m²n(x-y)的四次方=mn(x-y)³(n+m(x-y))=mn(x-y)³(n+mx-my)分解因式xy²-2xy+2y-4xy²-2xy+2y-4=xy(y-2)+2(y-2)=(xy+2)(y-2)