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