• 试题 ID 40281


设 $f\left(\frac{y}{x}, x+y\right)=x^2-y^2$ ,则 $f(x, y)=(\quad)$ .
A $\frac{y^2(1-x)}{1+x}$
B $\frac{x^2(1-x)}{1+y}$
C $\frac{y^2(1-y)}{1+x}$
D $\frac{x^2(1-y)}{1+y}$
E
F
答案:

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解析:

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