已知3/x-2/y=3 则2x-3y-xy/7xy+9y-6x 等于?如题
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已知3/x-2/y=3 则2x-3y-xy/7xy+9y-6x 等于?如题
已知3/x-2/y=3 则2x-3y-xy/7xy+9y-6x 等于?
如题
已知3/x-2/y=3 则2x-3y-xy/7xy+9y-6x 等于?如题
3/x-2/y=3
所以x!=0,y!=0
所以xy!=0,原式分子分母同除xy得,
(2x-3y-xy)/(7xy+9y-6x)
=(2/y-3/x-1)/(7+9/x-6/y)
=(-(3/x-2/y)-1)/(7+3(3/x-2/y))
=(-3-1)/(7+3*3)
=-4/16
=-1/4
要求的式子分子分母同时除以xy得
(2/y-3/x-1)/(7+9/x-6/y)
由已知得7+9/x-6/y=9
则答案为-1/4
原式=(2/y-3/x-1)/(7+9/x-6/y)=(-3-1)/(7+9)=-1/4
因为3/x-2/y=3
所以3y-2x/xy=3 所以3y-2x=3xy
因为2x-3y-xy/7xy+9y-6x =-(3y-2x+xy)/7xy+3(3y-2x)
将3y-2x=3xy带入
得-1/4
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