\[\sqrt{2x - 8} \leq 2\]
\[t = 2x - 8\]
\[\sqrt{t} \leq 2\]
\[0 \leq t \leq 4 \Longrightarrow 0 \leq 2x - 8 \leq 4\]
\[\left\{ \begin{matrix} 2x - 8 \geq 0 \\ 2x - 8 \leq 4 \\ \end{matrix} \right.\ \text{\ \ \ \ \ \ \ \ }\]
\[\left\{ \begin{matrix} 2x \geq 8\ \ \ \\ 2x \leq 12 \\ \end{matrix} \right.\ \text{\ \ \ \ \ \ \ \ }\]
\[\left\{ \begin{matrix} x \geq 4 \\ x \leq 6 \\ \end{matrix} \right.\ \]
\[Ответ:\lbrack 4;6\rbrack\text{.\ }\]