已知1÷x-1÷y=-3,则(5x+xy-5y)÷(x-xy-y)的值为( )
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已知1÷x-1÷y=-3,则(5x+xy-5y)÷(x-xy-y)的值为( )
已知1÷x-1÷y=-3,则(5x+xy-5y)÷(x-xy-y)的值为( )
已知1÷x-1÷y=-3,则(5x+xy-5y)÷(x-xy-y)的值为( )
1÷x-1÷y=-3
则(y-x)÷(xy)=-3
所以y-x=-3xy
所以x-y=3xy
(5x+xy-5y)÷(x-xy-y)
=(5(x-y)+xy)÷((x-y)-xy)
=(15xy+xy)÷(3xy-xy)
=16xy÷(2xy)
=8
4 由已知可知xy=(x-y)/3 代入就可知了
∵1/x-1/y=-3
∴y-x=-3xy(去分母)
即x-y=3xy
∴要求的式子=[5(x-y)+xy]/[x-y-xy]=16xy/2xy=8
(5x+xy-5y)÷(x-xy-y)
分子分母同除以xy
=[-5((1/x)-(1/y))+1]/[-((1/x)-(1/y))-1]
=(15+1)/(3-1)
=8
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