Question

What is the sum of the geometric sequence 1,3,9, ... if there are 13 terms​

Answer 1

The answer is 797,161

Explanation:

This one is fairly easy if tedious.

How do you get from to 3 from 1? (multiply 1 by 3).

How do you get to 9 from 3? (multiply 3 by 3).

Then simply multiply each successive result by 3 until you have 13 results. Then add those 13 results.