Question 9 If $f(x, y)=x e^{x^{2}+y^{2}}$, then $f_{y}=$

Step 1 ：Given the function \(f(x, y)=x e^{x^{2}+y^{2}}\), we want to find the partial derivative of the function with respect to \(y\).

Step 2 ：The partial derivative of the function with respect to \(y\) is \(f_{y} = 2yx e^{x^{2}+y^{2}}\).

Step 3 ：So, the final answer is \(\boxed{2yx e^{x^{2}+y^{2}}}\).