\[\boxed{\text{343\ (343).\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
\[y = - 6x^{2} + x + c\]
\[\text{M\ }(0;\ - 8):\]
\[- 6 \cdot 0 + 0 + c = - 8\]
\[c = - 8\]
\[Ответ:\ c = - 8.\]