\[\boxed{\text{650\ (}\text{с}\text{).}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
\[\textbf{а)}\ c_{1} = - 4,\ \ q = 3,\ \ \]
\[S_{9} = c_{1} \cdot \frac{q^{9} - 1}{q - 1} = - 4 \cdot \frac{3^{9} - 1}{3 - 1} = - 2 \cdot 19682 = - 39\ 364.\]
\[\textbf{б)}\ c_{1} = 1,\ \ q = - 2,\]
\[S_{9} = c_{1} \cdot \frac{q^{9} - 1}{q - 1} = \frac{( - 2)^{9} - 1}{- 2 - 1} = \frac{513}{3} = 171.\]
\[Ответ:а) - 39364;\ \ б)\ 171.\]