若1/x-1/y=3,5x+3xy-5y/3x-xy-3y
问题描述：
若1/x-1/y=3,5x+3xy-5y/3x-xy-3y
答
1/x-1/y=(y-x)/xy=3
所以y-x=3xy
x-y=-3xy
所以原式=[5(x-y)+3xy]/[3(x-y)-xy]
=[5(-3xy)+3xy]/[3(-3xy)-xy]
=-12xy/(-10xy)
=6/5