[单选题]设f(x+y,y/x)=x2-y2(y≠-1),则f(x,y)等于()

A
y2[(1-x2)/(1+y)2
B
x(1-y2)/(1+y)2
C
x2(1-y)2/(1+y)2
D
y(1-x2)/(1+y)2
正确答案:C
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