已知x+y分之xy=2,那么3x-5xy+3y分之 - 知识问答

已知x+y分之xy=2,那么3x-5xy+3y分之3xy-x-y=

2个回答

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

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