For this sequence $5,25,125,625, …$. 

1. What kind of sequence is it?

   Hint (a):

   What mathematical operation do you use to find the next term?

   Answer (a):

   Geometric.

2. Find the fifth term, $a_{5}$.

   Answer (b):

   $3{,}125$

3. Write an explicit equation for the general term, $a_{n} =$ ?