Đáp án:
$\begin{array}{l}
E = \sqrt {3 - 2{x^2}} \\
Do:{x^2} \ge 0\\
\Leftrightarrow - 2{x^2} \le 0\\
\Leftrightarrow 3 - 2{x^2} \le 3\\
Dkxd:\sqrt {3 - 2{x^2}} \ge 0\\
\Leftrightarrow 0 \le \sqrt {3 - 2{x^2}} \le \sqrt 3 \\
\Leftrightarrow 0 \le E \le \sqrt 3 \\
\Leftrightarrow \left\{ \begin{array}{l}
GTLN:E = \sqrt 3 \,khi:x = 0\\
GTNN:E = 0\,khi:{x^2} = \dfrac{3}{2} \Leftrightarrow x = \pm \dfrac{{\sqrt 6 }}{2}
\end{array} \right.
\end{array}$
