已知1/x-1/y=-3,则x+5xy-y/3x-2xy-3y=

问题描述:

已知1/x-1/y=-3,则x+5xy-y/3x-2xy-3y=

(x+5xy-y)/(3x-2xy-3y)
分子分母同时除以xy,得:
=[(1/y-1/x)+5]/[3(1/y-1/x)-2]
=(3+5)/(3*3-2)
=8/7