求解求解!谢谢啦

Question

如题所述

Answer 1

1/x-1/y=3
(y-x)/(xy)=3
y-x=3xy
x-y=-3xy
(2x+y-x-2y)/(x-xy-y)
=(x-y)/[(x-y)-xy]
=-3xy/[-3xy-xy]
=3/4

Answer 2

解如下图所示