[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}\\
----------\\
n=4\\
a_1=-2\\
r=-5
\end{cases}\implies a_4=-2(-5)^{4-1}[/tex]
