计算：x+2y/x-y+2x/y-x-3y/x-y
问题描述：
计算：x+2y/x-y+2x/y-x-3y/x-y
答
答案是（-2xy^2-y^2+2x^2）/(xy)
答
原式=(x+2y)/(x-y)-2x/(x-y)-3y/(x-y)
=(x+2y-2x-3y)/(x-y)
=(-x-y)/(x-y)