Recursive and Explicit Equations...How to Write Them?

Hi,

I have been struggling with understanding these equations, searching for a way to simplify them. My professor makes them seem impossible, and I don't understand her teaching methods...so going to her for help, isn't really an option. I have been researching for a different way to do them, but I just cannot figure it out. Help!!

Here is a problem I am working on...if you could give me an example of something similar (I would rather find the answer to this one on my own!(Happy)).

Suppose that a population grows according to a linear growth model. The initial population is 200, and it grows by 25 every month.

--Write a recursive equation that can be used to find the population at the end of any month.

--Write an explicit equation that can be used to find the population at the end of any month.

Thank you for any help you can give me!!!(Happy)