[tex]n^{th}\textit{ term of an arithmetic sequence} \\\\ a_n=a_1+(n-1)d\qquad \begin{cases} a_n=n^{th}\ term\\ n=\textit{term position}\\ a_1=\textit{first term}\\ d=\textit{common difference}\\[-0.5em] \hrulefill\\ a_1=9\\ d=-2 \end{cases} \\\\\\ a_n=9+(n-1)(-2)\implies a_n=9-2n+2\implies a_n=11-2n[/tex]
