Math Is Fun Forum

LuisRodg

Real Member

Registered: 2007-10-23

Posts: 322

population model

lets say you have a population with a initial population at time zero of 15000. This population decreases 5% of last year's population and increases a flat amount of 400 every year.

So you can write it recursively:

f(t) =0.95f(t-1)+400

How do you write it in closed form?

Daniel123

Member

Registered: 2007-05-23

Posts: 663

Re: population model

Seeing as each term is defined in terms of the term before it, we should write out a few iterations:

Now subsitute these in.

You can now evaluate the sum of the geometric series:

Last edited by Daniel123 (2008-11-02 13:24:51)