已知x+y分之xy=2,那么3x-5xy+3y分之3xy-x-y=

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已知x+y分之xy=2,那么3x-5xy+3y分之3xy-x-y=
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已知x+y分之xy=2,那么3x-5xy+3y分之3xy-x-y=
已知x+y分之xy=2,那么3x-5xy+3y分之3xy-x-y=

已知x+y分之xy=2,那么3x-5xy+3y分之3xy-x-y=
xy/(x+y)=2
∴xy=2(x+y)
(3xy-x-y)/(3x-5xy+3y)
=[6(x+y)-x-y]/[3x+3y-10(x+y)]
=5(x+y)/[-7(x+y)]
=-5/7

2(X+Y)=XY
3XY-X-Y/3X-5XY+3Y
=3XY-(X+Y)/3(X+Y)-5XY
=6(x+y)-(x+y)/3(x+y)-5*2(x+y)
=5(x+y)/(-7)(x+y)
=-5/7