已知(xy)/(x+y)=6求(3x-2xy+3y)/(-x+3xy-y)的值.

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已知(xy)/(x+y)=6求(3x-2xy+3y)/(-x+3xy-y)的值.

已知(xy)/(x+y)=6求(3x-2xy+3y)/(-x+3xy-y)的值.
已知(xy)/(x+y)=6求(3x-2xy+3y)/(-x+3xy-y)的值.

已知(xy)/(x+y)=6求(3x-2xy+3y)/(-x+3xy-y)的值.
由(xy)/(x+y)=6得xy=6(x+y)
所以(3x-2xy+3y)/(-x+3xy-y)
=[3x-2×6(x+y)+3y]/[-x+3×6(x+y)-y]
=-9(x+y)/[17(x+y)]
=-9/17
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-9/17

xy=6(x+y)带入二式 (3x-2*6(x+y)+3y)/(-x+3*6(x+y)-y)=-9/17