Question

what is the the sum of the geometric sequence -3 21 147 if there are 6 terms?

Answer 1

well one way to do it is find all six terms and then add them up

Answer 2

Geometric sequences have a common ratio.
When you think ratio, think division.
What is second term/first term?
In other words what is 21/3?

Answer 3

You will see that this is the common ratio because 147/21 will give you the same as 21/3

Answer 4

This common ratio number is the number you would multiply to the third term to figure out the fourth term.
And so on...

Answer 5

Thanks I got it!