1、5a平方b（x-y）3次方-30ab平方（y-x）平方
=5a²b(x-y)³-30ab(x-y)²
=5ab(x-y)²[a(x-y)-6]
=5ab(x-y)²(ax-ay-6)
2、 （x平方+y平方）平方-4x平方y平方
=(x²+y²+2xy)(x²+y²-2xy)
=(x+y)²(x-y)²