Identify whether these series are divergent or convergent geometric series and find the sum, if possible.

A geometric series:

It's convergent if |r|<1.
It's divergent if |r|≥1.
The sum can be found if it's a convergent series; it's equal to .

3.


The answer is: This is a convergent geometric series. The sum is 30.

4.


The answer is: This is a divergent geometric series. The sum cannot be found.