Is the sequence geometric? if so, identify the common ratio 1/5,2/15,4/45,8/135,16/

So have the sequence: 
To check if the sequence is geometric, we are going to find its common ratio; to do it we are going to use the formula: 
where 
is the common ratio 
is the current term in the sequence 
is the previous term in the sequence
In other words we are going to divide the current term by the previous term a few times, and we will to check if that ratio is the same:

For  and :



For  and :



For  and :


As you can see, we have a common ratio!

We can conclude that our sequence is a geometric sequence and its common ratio is  

Ithink the answer is a