如果1\x-1\y=2,那么3x+5xy-3y\x-xy-y等于多少这是初二的数学题分式那一张的,有知道的请帮帮我,

如果1\x-1\y=2,那么3x+5xy-3y\x-xy-y等于多少这是初二的数学题分式那一张的,有知道的请帮帮我,
如果1\x-1\y=2,那么3x+5xy-3y\x-xy-y等于多少
这是初二的数学题分式那一张的,有知道的请帮帮我,

如果1\x-1\y=2,那么3x+5xy-3y\x-xy-y等于多少这是初二的数学题分式那一张的,有知道的请帮帮我,
1/x-1/y=2
(y-x)/xy=2
y-x=2xy
(3x+5xy-3y)/(x-xy-y)
=[5xy-3(y-x)]/[-xy-(y-x)]
=(5xy-6xy)/(-xy-2xy)
=-xy/-3xy
=1/3

1/x-1/y=2
同时乘以xy
y-x=2xy
x-y=-2xy
[3(x-y)+5xy]/[(x-y)-xy]
=(-6xy+5xy)/(-2xy-xy)
=(-xy)/(-3xy)
=1/3

通分得y-x=2xy，将xy=(y-x)/2代入分式得[3(x-y)-5/2(x-y)]/[(x-y)+(x-y)/2] = 1/3