\[Теорема\ Виета:\]
\[\left\{ \begin{matrix} x_{1} + x_{2} = - b \\ x_{1} \cdot x_{2} = c\ \ \ \ \ \ \\ \end{matrix} \right.\ \]
\[\sqrt{13}\ \ и\ \ - \sqrt{13}:\]
\[x_{1} + x_{2} = \sqrt{13} - \sqrt{13} = 0;\]
\[x_{1} \cdot x_{2} = \sqrt{13} \cdot \left( - \sqrt{13} \right) = - 13.\]
\[Уравнение:\ \]
\[x^{2} + 0 \cdot x - 13 = 0 \Longrightarrow\]
\[\Longrightarrow x^{2} - 13 = 0.\]