The population P(t) of a species satisfies the logistic differential equation dP/dt= P(2-(P/5000)) where the initial population 3,000 and t is the time in years. What is the lim t>infinity P(t)?

Respuesta :

A logistic differential equation can be written as follows:
[tex] \frac{dP}{dt} = rP[1- \frac{P}{K}] [/tex]

where r = growth parameter and K = carrying parameter.

In order to write you equation in this form, you have to regroup 2:
[tex] \frac{dP}{dt} = 2P[1- \frac{P}{10000}] [/tex]

Therefore, in you case r = 2 and K = 10000

To solve the logistic differential equation you need to solve:

[tex] \int { \frac{1}{[P(1- \frac{P}{K})] } } \, dP = \int {r} \, dt [/tex]

The soution will be:

P(t) = [tex] \frac{P(0)K}{P(0)+(K-P(0)) e^{-rt} } [/tex]

where P(0) is the initial population.

In your case, you'll have:

P(t) = [tex] \frac{3E7}{3E3+7E3 e^{-2t} } [/tex]

Now you have to calculate the limit of P(t).
We know that
[tex] \lim_{t \to \infty} e^{-2t} -\ \textgreater \ 0 [/tex]

hence,

[tex] \lim_{t \to \infty} P(t) = \lim_{t \to \infty} \frac{3E7}{3E3+0} = 10^{4} [/tex]