1/x-1/y=3
同时乘以xy
y-x=3xy
x-y=-3xy
(2x-3xy-2y)/(x-2xy-y)
=[2(x-y)-3xy]/[(x-y)-2xy]
=(-6xy-3xy)/(-3xy-2xy)
=(-9xy)/(-5xy)
=9/5