已知1/x-1/y=5、求分式3x+5xy-3y/y-xy-x的值
问题描述：
已知1/x-1/y=5、求分式3x+5xy-3y/y-xy-x的值
答
1/x-1/y=(y-x)/xy=5
y-x=5xy
x-y=-5xy
原式=]3(x-y)+5xy]/[(y-x)-xy]
=[3(-5xy)+5xy]/[(5xy)-xy]
=-10xy/(4xy)
=-5/2