1/x-1/y=3,则求3y+xy-3x/2x-xy-2y

问题描述:

1/x-1/y=3,则求3y+xy-3x/2x-xy-2y

y-x=3xy
(3y+xy-3x)/(2x-xy-2y)=10xy/(-7xy)=10/7