\[Теорема\ Виета:\]
\[\left\{ \begin{matrix} x_{1} + x_{2} = - b \\ x_{1} \cdot x_{2} = c\ \ \ \ \ \ \\ \end{matrix} \right.\ \]
\[2 - \sqrt{11}\ \ и\ \ 2 + \sqrt{11}:\]
\[x_{1} + x_{2} =\]
\[= 2 - \sqrt{11} + 2 + \sqrt{11} = 4;\]
\[x_{1} \cdot x_{2} = \left( 2 - \sqrt{11} \right)\left( 2 + \sqrt{11} \right) =\]
\[= 4 - 11 = - 7.\]
\[Уравнение:\ \]
\[x^{2} - 4x - 7 = 0.\]