Решебник по алгебре 9 класс Макарычев Задание 655

\[\boxed{\text{655}\text{\ (655)}\text{.}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]

\[x_{1} = 2,\ \ x_{5} = x_{1} \cdot q^{4} = 162,\ \ q < 0;\]

\[162 = 2q^{4},\ \ q^{4} = 81,\ \ q = - 3;\]

\[S_{6} = 2 \cdot \frac{( - 3)^{6} - 1}{- 3 - 1} = - \frac{728}{2} = - 364.\]

\[Ответ: - 364.\]

\[\boxed{\text{655.}\text{\ }\text{ОК\ ГДЗ\ -\ домашка\ на\ 5}}\]

\[x_{10} = x_{1} + 9d = 1\]

\[S_{16} = \frac{2x_{1} + 15d}{2} \cdot 16 =\]

\[= 8 \cdot \left( x_{1} + x_{1} + 15d \right) =\]

\[= 2 \cdot \left( 2x_{1} + 15d \right) = 4\]

\[\left\{ \begin{matrix} x_{1} + 9d = 1\ \ \ \ \\ 4x_{1} + 30d = 1 \\ \end{matrix} \right.\ \Longrightarrow\]

\[\Longrightarrow \left\{ \begin{matrix} x_{1} = 1 - 9d\ \ \ \ \ \ \ \ \ \ \ \ \ \\ 4 - 36d + 30d = 1 \\ \end{matrix} \right.\ \Longrightarrow\]

\[\Longrightarrow \left\{ \begin{matrix} x_{1} = 1 - 9d \\ - 6d = - 3\ \ \ \\ \end{matrix} \right.\ \Longrightarrow\]

\[\Longrightarrow \left\{ \begin{matrix} d = 0,5\ \ \ \ \ \\ x_{1} = - 3,5. \\ \end{matrix} \right.\ \]