## anonymous one year ago What is the sum of the geometric sequence 4, 12, 36 . if there are 9 terms?

1. freckles

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

2. anonymous

Thanks a lot freckles ~~

3. anonymous

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