\[\boxed{\mathbf{715\ (715).\ }Еуроки\ - \ ДЗ\ без\ мороки}\]
\[x_{2} = ?\]
\[x² - 8x + q = 0\]
\[\left\{ \begin{matrix} x_{1} + x_{2} = 8 \\ x_{1} \cdot x_{2} = q \\ x_{1} = - 2\ \ \ \ \ \\ \end{matrix} \right.\ \]
\[x_{2} = 8 - x_{1}\]
\[x_{2} = 8 + 2 = 10\]
\[x_{1} \cdot x_{2} = - 2 \cdot 10 = - 20\]
\[q = - 20\]
\[Ответ:x_{2} = 10;\ \ q = - 20.\]