设函数f(x,y)=xy/(x-y),则f(1/y,1/x)=()
设函数f(x,y)=xy/(x-y),则f(1/y,1/x)=()
A、1/(y-x)
B、(x-y)/yx
C、1/(x-y)
D、x2y2/(x-y)
【正确答案】:C
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