Question

计算xy-y的平方分之(x-y)的平方÷xy-y的平方分之xy+y的平方÷x-y分之y

{xy分之（x的平方+y的平方）-（xy+y的平方）分之x的平方-(x的平方+xy)分之y的平方}除以xy分之3

Answer 1

[(x²+y²)/xy-x²/(xy+y²)-y²/(x²xy)]÷(3/xy)
=[(x²+y²)(x+y)-x³-y³]/xy(x+y)×(xy/3)
=(x²y+xy²)/[3(x+y)]
=xy(x+y)/[3(x+y)]
=xy/3