\[\boxed{\text{810\ (810).\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
\[y = x^{2} - 8x\ \ \ и\ \ \ \ y = 4 - 8x\]
\[x^{2} - 8x = 4 - 8x\]
\[x^{2} = 4\]
\[x^{2} - 4 = 0\]
\[(x - 2)(x + 2) = 0\]
\[x = 2\ \ \ \ \ \ или\ \ \ \ \ x = - 2\]
\[Ответ:\ x = \pm 2.\]