\[b_{1} = 8;\ \ b_{4} = - 64:\]
\[8;\ \ b_{1}q;\ \ b_{1}q^{2};\ - 64\]
\[8q^{3} = - 64\]
\[q^{3} = - 8\]
\[q = - 2.\]
\[b_{1}q = 8 \cdot ( - 2) = - 16;\ \]
\[b_{1}q^{2} = 8 \cdot ( - 2)^{2} = 32.\]
\[Ответ:числа\ - 16;32.\]