原式=2xy/[xy(x-y)]+x²(x-y)/[xy(x-y)]-y(x-y)/[xy(x-y)]=[2xy+x²(x-y)-y(x-y)]/[xy(x-y)]=(2xy+x³-x²y-xy+y²)/[xy(x-y)]=(x³-x²y+xy+y²)/[xy(x-y)]