ГДЗ по алгебре 9 класс Макарычев Задание 580

\[\boxed{\text{580}\text{\ (580)}\text{.}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]

\[\textbf{а)} - 8;\ - 6,5;\ldots\]

\[a_{1} = - 8;\ \ \ a_{2} = - 6,5;\]

\[d = a_{2} - a_{1} = - 6,5 - ( - 8) =\]

\[= 8 - 6,5 = 1,5;\]

\[a_{n} = - 8 + 1,5 \cdot (n - 1);\]

\[a_{23} = - 8 + 1,5 \cdot (23 - 1) =\]

\[= - 8 + 33 = 25.\]

\[\textbf{б)}\ 11;7;\ldots\ \]

\[a_{1} = 11;\ \ a_{2} = 7;\]

\[d = a_{2} - a_{1} = 7 - 11 = - 4;\]

\[a_{n} = 11 - 4 \cdot (n - 1);\]

\[a_{23} = 11 - 4 \cdot (23 - 1) =\]

\[= 11 - 88 = - 77.\]