3. We go back to the logistic model for population dynamics (without harvesting), but we now allow the growth rate and carrying capacity to vary in time: dP P k(t)P dt M(t) In this case the equation is not autonomous, so we can't use phase line analysis. We will instead find explicit analytical solutions. (a) Show that the substitution z = 1/P transforms the equation into the linear equation Pz=) KIt).! (1- dz k(t) + k(t)z = M(t) dt ZMA) (b) Using your résult in (a), show that if k is constant but M varies, the general solution is KH)ZMH)-) ekt (P)- 4)= =") mo P(t) = C + S Modt kekt %3D ZMA) (c) Similarly, show that if M is constant but k varies, the general solution is M P(t) 1+ CMe-Sk(t) dt " (d) Consider the special case where M is constant but k decreases in time as k = e-t. Suppose that the initial population is less than M. What happens to the population in the long run? Does it make sense?

Advanced Engineering Mathematics
10th Edition
ISBN:9780470458365
Author:Erwin Kreyszig
Publisher:Erwin Kreyszig
Chapter2: Second-order Linear Odes
Section: Chapter Questions
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Part c plz
3. We go back to the logistic model for population dynamics (without harvesting), but we now allow the
growth rate and carrying capacity to vary in time:
dP
P
= k(t)P(1-
dt
M(t)
In this case the equation is not autonomous, so we can't use phase line analysis. We will instead find
explicit analytical solutions.
(a) Show that the substitution z = 1/P transforms the equation into the linear equation
2= ]
KIH) ! (1-
dz
+ k(t)z =
dt
k(t)
M(t)
ZMP)
(b) Using your résult in (a), show that if k is constant but M varies, the general solution is
KH) ZMA)-)
(P)- {4)=)
ekt
P(t)
C + S Modt
kekt
ZMA)
(c) Similarly, show that if M is constant but k varies, the general solution is
M
P(t) =
1+ CMe-Sk(t)dt "
(d) Consider the special case where M is constant but k decreases in time as k = e=t. Suppose that the
initial population is less than M. What happens to the population in the long run? Does it make
sense?
Transcribed Image Text:3. We go back to the logistic model for population dynamics (without harvesting), but we now allow the growth rate and carrying capacity to vary in time: dP P = k(t)P(1- dt M(t) In this case the equation is not autonomous, so we can't use phase line analysis. We will instead find explicit analytical solutions. (a) Show that the substitution z = 1/P transforms the equation into the linear equation 2= ] KIH) ! (1- dz + k(t)z = dt k(t) M(t) ZMP) (b) Using your résult in (a), show that if k is constant but M varies, the general solution is KH) ZMA)-) (P)- {4)=) ekt P(t) C + S Modt kekt ZMA) (c) Similarly, show that if M is constant but k varies, the general solution is M P(t) = 1+ CMe-Sk(t)dt " (d) Consider the special case where M is constant but k decreases in time as k = e=t. Suppose that the initial population is less than M. What happens to the population in the long run? Does it make sense?
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