Homework Statement
Let :
f(x,y) = \frac{xy(x^2 - y^2)}{(x^2 + y^2)^2} if (x,y) \neq (0,0)
f(x,y) = 0 if (x,y) = (0,0)
a) Find f_{xx}(0,0)
b) Find f_{xy}(0,0)
c) Find f_{yx}(0,0)
Homework Equations
None
The Attempt at a Solution
I'm not sure how to deal with the piecewise...