Exercise 2 Solution

(You may want to maximize your window to see the solution more clearly.)

We want to verify that

is a solution of the differential equation. But first, we will simplify the notation:

Let

Therefore,

 

Now find the derivative with respect to t,

 

Thus,

But we also have,

Simplifying and combining terms with a common denominator gives,

And finally,

which is the same as the right-hand side of equation (1); thus,

solves the given differential equation.

To examine the asymptotic behavior, we take the limit as time approaches infinity,

Because M and P0 are constants, only the exponential will be affected by the limit. Because r (the growth constant) is positive, then

Thus,

That is as expected (because M is the limiting population value that can be supported by assumption), the population is asymptotic to y = M.