We want to find the sum of the geometric series with the given characteristics.
a_1=15, r=2, and n=4To do so, we will substitute the above values into the formula for the sum of the first $n$ terms.
\begin{gathered}
S_n=\dfrac{a_1 - a_1 r^n}{1-r} \\
\Downarrow \\
S_n=\dfrac{\col{15} - \col{15} \left(\colIII{2}\right)^\colII{4}}{1-\colIII{2}}
\end{gathered}
Let's use the expression to find the value of $S_n.$
