\[\boxed{\text{720\ (720).}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
\[\textbf{а)}\ 4 - x(x + 8) = 11 - x^{2}\]
\[- 8x = 11 - 4\]
\[- 8x = 7\]
\[x = - \frac{7}{8}\]
\[Ответ:x = - \frac{7}{8}.\]
\[\textbf{б)}\ 4x(3x - 1) - 2x(6x + 8) = 5\]
\[- 20x = 5\]
\[x = - 0,25\]
\[Ответ:x = - 0,25.\]