\[b_{4} - b_{2} = 18;\ \ \ b_{5} - b_{3} = 36\]
\[b_{1} \cdot q^{3} - b_{1}q = 18\]
\[b_{1}\left( q^{3} - q \right) = 18\]
\[b_{1} = \frac{18}{q^{3} - q}.\]
\[b_{1} \cdot q^{4} - b_{1} \cdot q^{2} = 36\]
\[b_{1}\left( q^{4} - q^{2} \right) = 36\]
\[b_{1} = \frac{36}{q^{4} - q^{2}}.\]
\[\frac{18}{q^{3} - q} = \frac{36}{q^{4} - q^{2}}\]
\[18 \cdot \left( q^{4} - q^{2} \right) = 36 \cdot \left( q^{3} - q \right)\]
\[18q^{2}\left( q^{2} - 1 \right) = 36q\left( q^{2} - 1 \right)\]
\[18q^{2} = 36q\]
\[q = 2.\]
\[b_{1} = \frac{18}{8 - 2} = \frac{18}{6} = 3.\]
\[Ответ:q = 2;\ \ b_{1} = 3.\]