已知x分之1+y分之1=-2,则x+xy+y分之x-xy+y的值等于
问题描述：
已知x分之1+y分之1=-2,则x+xy+y分之x-xy+y的值等于
答
1/x+1/y=-2，所以(x+y)/(xy)=-2，即x+y=-2xy.
所以(x-xy+y)/(x+xy+y)
=(-2xy-xy)/(-2xy+xy)
=(-3xy)/(-xy)
=3.
答
1/x+1/y=-2
则
(x-xy+y)/(x+xy+y)
分子分母同除以xy
=(1/x+1/y-1)/(1/x+1/y+1)
=(-2-1)/(-2+1)
=3