-5a²b（x-y）^3 × ab(y-x)^4/15
=a^2b(y-x)^3 ×ab(y-x)^4÷3
=1/3a^3b^2(y-x)^7为什么1/3a^3b^2和(y-x)^7不乘开这是最简式啊Are you sure???????????????????????????????????????????????????????????????YES