[tex]\bf n^{th}\textit{ term of a geometric sequence}\\\\
a_n=a_1\cdot r^{n-1}\qquad
\begin{cases}
n=n^{th}\ term\\
a_1=\textit{first term's value}\\
r=\textit{common ratio}\\
----------\\
a_1=10\\
r=0.5\\
n=4
\end{cases}\implies a_4=10\cdot 0.5^{4-1}[/tex]
