已知2/x-1/y=3,则(2y-x+4xy)/(3x-6y-5xy)=?

已知2/x-1/y=3,则(2y-x+4xy)/(3x-6y-5xy)=?
已知2/x-1/y=3,则(2y-x+4xy)/(3x-6y-5xy)=?

已知2/x-1/y=3,则(2y-x+4xy)/(3x-6y-5xy)=?
2/x-1/y=3
2y-x=3xy
(2y-x+4xy)/(3x-6y-5xy)
=[(2y-x)+4xy]/(-3(2y-x)-5xy]
=(3xy+4xy)/(-9xy-5xy)
=7xy/(-14xy)
=-1/2

2/x-1/y=3
2y-x=3xy
(2y-x+4xy)/(3x-6y-5xy)
=7xy/-14xy=-1/2

-1/2
分子分母 同除xy可得到 关于2/x-1/y 的形式

2/X-1/Y=3 两边乘XY
2Y-X=3XY
原式=(3XY+4XY)/(-9XY-5XY)=-1/2