A sequence $\left\{ a _ { n } \right\}$ satisfies the following conditions. (가) $a _ { 1 } = a _ { 2 } + 3$ (나) $a _ { n + 1 } = - 2 a _ { n } ( n \geq 1 )$ Find the value of $a _ { 9 }$. [3 points]
A sequence $\left\{ a _ { n } \right\}$ satisfies the following conditions.\\
(가) $a _ { 1 } = a _ { 2 } + 3$\\
(나) $a _ { n + 1 } = - 2 a _ { n } ( n \geq 1 )$\\
Find the value of $a _ { 9 }$. [3 points]