The question is:

Evaluate $\displaystyle f_{xy}(0, 0)$ and $\displaystyle f_{yx}(0, 0)$ for $\displaystyle f(x, y) = xy\frac{x^2−y^2}{x^2+y^2}$.

What would you say about Clairaut's theorem?

I found fxy(x,y) but then I realized... wouldn't this be undefined if you evaluate at f(0,0)?

Thanks.