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已知x分之1—y分之1=3,求x-2xy-y分之5x+3xy-5y的值,
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已知x分之1—y分之1=3,求x-2xy-y分之5x+3xy-5y的值,
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1/x-1/y=3(y-x)/xy=3y-x=3xyx-y=-3xy所以原式=[5(x-y)+3xy]/[(x-y)-2xy]=(-15xy+3xy)/(-3xy-2xy)=(-12xy)/(-5xy)=12/5 法二:5x+3xy-5y/x-2xy-y上下同时除以xy(5/y+3-5/x)/(1/y-2-1/x)=(-5(1/x-1/y)+3)/(-(1/x-1/y)-...
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