ГДЗ по алгебре 9 класс Макарычев Задание 631

\[\boxed{\text{631.}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]

\[\textbf{а)}\ c_{5} = c_{1} \cdot q^{4} = - 6,\ \ c_{7} = c_{1} \cdot q^{6} = - 54,\ \]

\[\Longrightarrow \frac{c_{1} \cdot q^{6}}{c_{1} \cdot q^{4}} = \frac{- 54}{- 6};\ \ \ \ q^{2} = 9,\ \ q = \pm 3.\]

\[\textbf{б)}\ c_{6} = c_{1} \cdot q^{5} = 25,\ \ c_{8} = c_{1} \cdot q^{7} = 4,\ \]

\[\frac{c_{8} \cdot q^{7}}{c_{6} \cdot q^{5}} = \frac{4}{25},\ \ q² = \frac{4}{25},\ \ q = \pm \frac{2}{5}.\]