若xy/x+y=2,则3x-xy+3y/-x+3xy-y=

问题描述:

若xy/x+y=2,则3x-xy+3y/-x+3xy-y=

∵xy/(x+y)=2,即xy=2x+2y,
∴(3x-xy+3y)/(-x+3xy-y)=(3x-2x-2y+3y)/(-x+6x+6y-y)=(x+y)/5(x+y)=1/5。

原题是 xy/(x+y)=2 求(3x-xy+3y)/(-x+3xy-y)吗 如果是 那么计算如下由xy/(x+y)=2 得x+y=xy/2(3x-xy+3y)/(-x+3xy-y=[3(x+y)-xy]/[-(x+y)+3xy]=[3xy/2-xy]/[-xy/2+3xy]=(xy/2)/(5xy/2)=xy/2×2/5x...