\[16,\ \ \ b_{2},\ \ \ b_{3},\ \ \ b_{4},\ \ \ 81\]
\[b_{5} = b_{1} \cdot q^{4}\text{\ \ \ \ \ }\]
\[q^{4} = \frac{b_{5}}{b_{1}} = \frac{81}{16}\text{\ \ \ \ \ }\]
\[q = \pm \frac{3}{2}.\]
\[При\ q = 1,5:\]
\[b_{2} = 16 \cdot \frac{3}{2} = 24,\ \ \ \ \]
\[b_{3} = 24 \cdot \frac{3}{2} = 36,\ \ \ \ \ \ \]
\[b_{4} = 36 \cdot \frac{3}{2} = 54.\]
\[При\ q = - 1,5:\]
\[b_{2} = 16 \cdot \left( - \frac{3}{2} \right) = - 24,\ \ \ \]
\[b_{3} = - 24 \cdot \left( - \frac{3}{2} \right) = 36,\ \ \]
\[b_{4} = 36 \cdot \left( - \frac{3}{2} \right) = - 54.\]
\[Ответ:24,\ \ \ 36,\ \ \ 54\ \ \ \]
\[или\ - 24,\ \ \ 36, - 54.\]