1/x+1/y=4,则(3x+xy+3y)/(x-xy+3y)=

问题描述:

1/x+1/y=4,则(3x+xy+3y)/(x-xy+3y)=

分子分母同时除以xy得
原式=(3/y+1+3/x )/ (1/y-1+1/x)
=(3*4+1)/(4-1)
=13/3