\[f(x) = \sqrt{x + 3} + \frac{x + 2}{x² - 9},\ \ \]
\[\left\{ \begin{matrix}
x + 3 \geq 0 \\
x^{2}
eq 9\ \ \ \ \ \ \\
\end{matrix} \right.\ \text{\ \ \ \ \ \ \ \ }\left\{ \begin{matrix}
x \geq - 3\ \ \ \\
x
eq = \pm 3 \\
\end{matrix} \right.\ \]
\[\Longrightarrow D(f) = ( - 3;3) \cup (3;\ + \infty).\]