已知xy/x+y=2,求代数式8x-5xy+8y/-x+3xy-y的值

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已知xy/（x+y）=2,即x+y=xy/2. 8x-5xy+8y/(-x+3xy-y) =8(x+y)-5xy/(3xy-(x+y)) =-xy/2.5xy =-2.5