已知1/x - 1/y = 2,求3x+7xy-3y / 2x-3xy-2y的值1/x-1/y=2(y-x)/xy=2 得：x-y=-2xy(3x+7xy-3y)/(2x-3xy-2y)=[3(x-y)+7xy]/[2(x-y)-3xy]=(-6xy+7xy)/(-4xy-3xy)=xy/(-7xy)=-1/71/x-1/y=2到(y-x)/xy=2 是怎么变化的..

已知1/x - 1/y = 2,求3x+7xy-3y / 2x-3xy-2y的值1/x-1/y=2(y-x)/xy=2 得：x-y=-2xy(3x+7xy-3y)/(2x-3xy-2y)=[3(x-y)+7xy]/[2(x-y)-3xy]=(-6xy+7xy)/(-4xy-3xy)=xy/(-7xy)=-1/71/x-1/y=2到(y-x)/xy=2 是怎么变化的..
已知1/x - 1/y = 2,求3x+7xy-3y / 2x-3xy-2y的值
1/x-1/y=2
(y-x)/xy=2 得：x-y=-2xy
(3x+7xy-3y)/(2x-3xy-2y)
=[3(x-y)+7xy]/[2(x-y)-3xy]
=(-6xy+7xy)/(-4xy-3xy)
=xy/(-7xy)
=-1/7
1/x-1/y=2到(y-x)/xy=2 是怎么变化的..

已知1/x - 1/y = 2,求3x+7xy-3y / 2x-3xy-2y的值1/x-1/y=2(y-x)/xy=2 得：x-y=-2xy(3x+7xy-3y)/(2x-3xy-2y)=[3(x-y)+7xy]/[2(x-y)-3xy]=(-6xy+7xy)/(-4xy-3xy)=xy/(-7xy)=-1/71/x-1/y=2到(y-x)/xy=2 是怎么变化的..
1/x-1/y通过普通加减法运算,先通分,则1/x=y/xy ,
1/y=x/xy.则1/x-1/y=(y-x)/xy=2.

通分

......
1/x-1/y=2
xy(1/x-1/y)=2xy 等号两边同时乘以xy
y-x=2xy 把左边的 xy乘进去
xy=（y-x）/2 把这个带入后面的分式思路更清楚一点