已知x的-1次方+y的-1次方=5,求分式(2x-xy+2y)/(x+2xy+y)的值.
问题描述：
已知x的-1次方+y的-1次方=5,求分式(2x-xy+2y)/(x+2xy+y)的值.
答
1/x+1/y=5
x+y=5xy
(2x-xy+2y)/(x+2xy+y)
=[2(x+y)-xy]/[(x+y)+2xy]
=9xy/7xy
=9/79xy/7xy是怎么得出来的？