\[\boxed{\text{682\ (682).}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
\[b \cdot ( - 2b) = - 2b\]
\[- 2b^{2} + 2b = 0\]
\[- 2b(b - 1) = 0\]
\[b_{1} = 0\ \ \ \ \ \ \ b_{2} = 1\]
\[c_{1} = - 2 \cdot 0 = 0\ \ (c \neq 0)\]
\[c_{2} = - 2 \cdot 1 = - 2.\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \]
\[Ответ:b = 1,\ c = - 2\text{.\ }\]
\[\boxed{\text{682.}\text{\ }\text{еуроки}\text{-}\text{ответы}\text{\ }\text{на}\text{\ }\text{пятёрку}}\]
\[\textbf{а)}\ (x - 5)(y + 6) = 0\ \]
\[две\ прямые:x = 5\ \ \ \ и\ \ y = - 6.\]
\[\textbf{б)}\ (x - 4)(x + 2) = 0\]
\[две\ прямые:\ \ x = 4\ \ и\ \ x = - 2.\]