\[2;\ \ \ b_{2};\ \ b_{3};\ \ - 54.\]
\[b_{4} = b_{1} - q^{3}\]
\[q^{3} = - \frac{54}{2} = - 27\]
\[q = - 3.\]
\[b_{2} = 2 \cdot ( - 3) = - 6;\ \ \]
\[b_{3} = - 6 \cdot ( - 3) = 18.\]
\[Ответ:\ - 6;18.\]