$\begin{array}{l}
F = \left\{ {1;\,\,\sqrt 2 ;\,\, - \sqrt 2 } \right\}\\
Ta\,\,\,co:\,\,\,\left( {x - 1} \right)\left( {{x^2} - 2} \right) = 0\\
\Leftrightarrow \left[ \begin{array}{l}
x = 1\\
{x^2} = 2
\end{array} \right. \Leftrightarrow \left[ \begin{array}{l}
x = 1\\
x = - \sqrt 2 \\
x = \sqrt 2
\end{array} \right.\\
\Rightarrow F = \left\{ {x|\,\,\left( {x - 1} \right)\left( {{x^2} - 2} \right) = 0} \right\}.
\end{array}$
