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[?] Find the critical solutions?

Posted 8 years ago

The question states, "Given that dP/dx=3P-2P^2 for the population P of a certain species at time t, find the critical solutions (equilibrium solutions)" I'm not exactly sure how to do that. I've tried using DSolveValue and Solve but they give two different answers so I'm not sure which one is right or if either are right. I'm new to mathematica so I don't know what to use

   In[3]:= (*2.1*)
DSolveValue[P'[x] == 3*P[x] - 2*P[x]^2, P, x]

Out[3]= Function[{x}, (3 E^(3 x))/(2 E^(3 x) + E^(3 C[1]))]
 In[6]:= Clear[P, x]
    Solve[P'[x] == 3*P[x] - 2*P[x]^2, P[x]]


    Out[7]= {{P[x] -> 1/4 (3 - Sqrt[9 - 8 Derivative[1][P][x]])}, {P[x] ->
    1/4 (3 + Sqrt[9 - 8 Derivative[1][P][x]])}}
POSTED BY: Brendan Isaac
3 Replies

The other solution is,

f = FullSimplify[P[x] /. DSolve[P'[x] == 3 P[x] - 2 P[x]^2, P[x], x][[1]]]

and

f /. x -> Infinity

It brings us the stable value

3/2

for all initial conditions.

POSTED BY: Takashi Yoshino
POSTED BY: Gianluca Gorni
Posted 8 years ago
POSTED BY: Bill Simpson
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