Question

What is the sum of the geometric sequence 4, 12, 36 . if there are 9 terms?

Answer 1

\[S_n=a \cdot \frac{1-r^n}{1-r} \text{ where } S_n \text{ represents the sum of the first } n \text{ terms }\]
\[a \text{ is the first term } \\ r \text{ is the common ratio }\]

Answer 2

Thanks a lot freckles ~~

Answer 3

Is there any work behind that or did you just follow the formula?