计算:(x+y分之3a的立方)的立方乘以(x的平方-y的平方)除以(y+x分之y-x)的2次方

[3a^3/(x+y)]^3*(x^2-y^2)/[(y-x)/(x+y)]^2
=27a^9/(x+y)^3*(x+y)*(x-y)*(x+y)^2/(x-y)^2
=27a^9/(x-y)