已知x分之1-y分之1=3,则代数式x-2xy-y分之5x+3xy-5y的值

问题描述:

已知x分之1-y分之1=3,则代数式x-2xy-y分之5x+3xy-5y的值

(5x+3xy-5y)/(x-2xy-y)
=(5/y+3-5/x)/(1/y-2-1/x)分子分母同时除以xy
=[-5(1/x-1/y)+3]/[-(1/x-1/y)-2]
=(-15+3)/(-3-2)
=12/5