\[b_{1} = 4;\ \ b_{4} = - 108:\]
\[4;\ \ b_{1}q;\ \ b_{1}q^{2};\ - 108\]
\[4q^{3} = - 108\]
\[q^{3} = - 27\]
\[q = - 3.\]
\[b_{1}q = 4 \cdot ( - 3) = - 12;\]
\[b_{1}q^{2} = 4 \cdot ( - 3)^{2} = 4 \cdot 9 = 36.\]
\[Ответ:числа\ - 12;\ 36.\]