Step 2
Next, find \( f_{y}(x, y) \).
\[
\begin{array}{l}
f_{y}(x, y)=\frac{\partial}{\partial y}\left(\frac{x}{x^{2}+y^{2}}\right) \\
=\frac{\left(\left(x^{2}+y^{2}\right) \cdot 0-20-2 x y\right)}{\left(x^{2}+y^{2}\right)^{2}} \\
=\frac{-2 \cdot x y}{\left(x^{2}+y^{2}\right)^{2}} \\
\end{array}
\]
Step 3
Therefore,
\[
\begin{aligned}
\nabla f(x, y) & =f_{x}(x, y) \hat{i}+f_{y}(x, y) j \\
& =\frac{y^{2}-x^{2}}{\left(x^{2}+y^{2}\right)^{2}} \mathbf{i}+\frac{-2 x y}{\left(x^{2}+y^{2}\right)^{2}} \mathbf{j} .
\end{aligned}
\]
The level curve for \( c=\frac{1}{4} \) is given by \( f(x, y)= \)