\[\frac{3b^{3} - 3b}{b^{2} + 7b + 6} = 0\]
\[b^{2} + 7b + 6 \neq 0\]
\[D = 49 - 24 = 25\]
\[b_{1} = \frac{- 7 - 5}{2} \neq - 6;\ \ \]
\[b_{2} = \frac{- 7 + 5}{2} \neq - 1.\]
\[3b^{3} - 3b = 0\]
\[3b\left( b^{2} - 1 \right) = 0\]
\[3b(b - 1)(b + 1) = 0\]
\[b = 0;\ \ b = 1;\ \ \]
\[b = - 1\ (не\ подходит)\]
\[Ответ:b = 0;\ \ b = 1.\]