Let me teach you some of the basics of a geometric series...

The difference between a sequence and a series is:

Series:

Sequence:

A geometric series is formed by multiplying each term by a constant.

For example:

Could also be written as:

The n-th term is equal to:

is the starting term, the first term (a = 1 in the example).

is the common ratio (r = 2 in the example).

You can determine with the following formula:

In series and sequences, the Sigma-sign is very important.

Now i do hope that's all...