Problem
Determine the domain of the function of two variables $f(x, y)=\sqrt{y+x}$. The domain is $\{(x, y)$ (Type an inequality. Use a comma to separate answers as needed. Use integers or fractions for any numbers in the inequality.)
Solution
Step 1 ：Determine the domain of the function of two variables $f(x, y)=\sqrt{y+x}$.
Step 2 ：The domain is the set of all $(x, y)$ that satisfy the inequality $x + y \geq 0$.
Step 3 ：\(\boxed{\text{The domain of the function is }\{(x, y) | x + y \geq 0\}}\)
