Differential Equations Problem, logistic models

beccajd
Messages
2
Reaction score
0

Homework Statement



Given that a population, P, after t months, can be modeled by the logistic model
dP/dt = .3 P (3.5 - P/40).
P(0) = 30

a) Solve the diff eq

b) Find the population after 2.5 months

c) Find lim P(t) as t -> infinity

Homework Equations



P(t) = P0 P1 /(P0 + (P1 - P0 )e^(-AP1 t))

A = k3 /2
P1 = (2k1 / k3 ) +1

The Attempt at a Solution


 
Physics news on Phys.org
hi, beccajd
You have pretty much done part a) already. You have written down the correct solution. So now you can work out what k1 and k3 should be, by looking at the numbers in the equation given to you. I think this is everything they expect from part a). Try doing part b), it shouldn't be too difficult, since you have got the equation for it.
 
There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...
Back
Top