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