\[f(x) = \sqrt{x + 2} - \sqrt{2 - x},\ \ \]
\[\left\{ \begin{matrix} x + 2 \geq 0 \\ 2 - x \geq 0 \\ \end{matrix} \right.\ \text{\ \ \ \ \ \ }\left\{ \begin{matrix} x \geq - 2 \\ x \leq 2\ \ \ \ \\ \end{matrix} \right.\ \]
\[D(f) = \lbrack - 2;2\rbrack.\]