\[b^{2} + 7b - 8 < 0\]
\[b_{1} + b_{2} = - 7,\ \ b_{1} \cdot b_{2} = - 8\]
\[b_{1} = - 8,\ \ b_{2} = 1\]
\[(b + 8)(b - 1) < 0\]
\[- 8 < b < 1.\]
\[Уравнение\ становится\ \]
\[линейным,\ если:\]
\[2b + 10 = 0\]
\[2b = - 10\]
\[b = - 5.\]
\[Ответ:( - 8; - 5) \cup ( - 5;1).\]