I'm not sure that your original function makes that much sense; I can't say that I can tell how you got to that point.
Just checking out how normal compounded interest works, I checked Wikipedia and rediscovered the formula:
$ A=P\bigg(1+\frac{r}{n}\bigg)^{nt} $
P = principal amount (initial investment)
r = annual nominal interest rate (as a decimal)
n = number of times the interest is compounded per year
t = number of years
A = amount after time t
I've tried to break that down into good 'ole
$ A=Pe^{rt} $
but haven't had any luck; I always end up with an indeterminate value relating one and infinity that I can't break down into something manageable with L'Hopital's.--Jmason 15:53, 2 October 2008 (UTC)