Answer:
The geometric series is where the ratio of consecutive terms is same.
We know that general representation of geometric series is:

So, we say a given geometric series is :
Convergent if |r|<1 and converges at a/1-r
Diverges if |r|>=1
Example:
We have a series: 2,4,8,16
Here the common ratio of the above series is :
Formula for common ratio: 
Here, 


So, the common ratio is 2> 1 so, series diverges.
Now, we have a series
16,8,4,2...



So, here r=1/2<1
Converging point is: a/1-r
Here, a=16, r=1/2 on substituting the values we get:

.