Case (i) If   [Graphics:Images/HarvestingModelProof_gr_18.gif]  there is one stationary solution [Graphics:Images/HarvestingModelProof_gr_19.gif].

    When  [Graphics:Images/HarvestingModelProof_gr_20.gif],  the differential equation has the form  [Graphics:Images/HarvestingModelProof_gr_21.gif]  and the solution is  

            [Graphics:Images/HarvestingModelProof_gr_22.gif].  

        

[Graphics:Images/HarvestingModelProof_gr_23.gif]

  

The solution with the initial condition  [Graphics:Images/HarvestingModelProof_gr_24.gif]  is

            [Graphics:Images/HarvestingModelProof_gr_25.gif].
        
If  [Graphics:Images/HarvestingModelProof_gr_26.gif]  then   [Graphics:Images/HarvestingModelProof_gr_27.gif].

If  [Graphics:Images/HarvestingModelProof_gr_28.gif]  then function  x(t)  has a vertical asymptote at  [Graphics:Images/HarvestingModelProof_gr_29.gif] and the population   x(t)  becomes extinct at some time  [Graphics:Images/HarvestingModelProof_gr_30.gif]  (where [Graphics:Images/HarvestingModelProof_gr_31.gif]),  i. e.  

            [Graphics:Images/HarvestingModelProof_gr_32.gif].

Proof (i).

There is one real roots of the characteristic equation  [Graphics:../Images/HarvestingModelProof_gr_33.gif],  it is  [Graphics:../Images/HarvestingModelProof_gr_34.gif].  

[Graphics:../Images/HarvestingModelProof_gr_35.gif]

[Graphics:../Images/HarvestingModelProof_gr_36.gif]

Thus there is one stationary solution  [Graphics:../Images/HarvestingModelProof_gr_37.gif].

We will verify that  [Graphics:../Images/HarvestingModelProof_gr_38.gif]  satisfies the D. E.  [Graphics:../Images/HarvestingModelProof_gr_39.gif].   

[Graphics:../Images/HarvestingModelProof_gr_40.gif]



[Graphics:../Images/HarvestingModelProof_gr_41.gif]
[Graphics:../Images/HarvestingModelProof_gr_42.gif]
[Graphics:../Images/HarvestingModelProof_gr_43.gif]
[Graphics:../Images/HarvestingModelProof_gr_44.gif]

[Graphics:../Images/HarvestingModelProof_gr_45.gif]

[Graphics:../Images/HarvestingModelProof_gr_46.gif]
[Graphics:../Images/HarvestingModelProof_gr_47.gif]

[Graphics:../Images/HarvestingModelProof_gr_48.gif]
[Graphics:../Images/HarvestingModelProof_gr_49.gif]
[Graphics:../Images/HarvestingModelProof_gr_50.gif]

[Graphics:../Images/HarvestingModelProof_gr_51.gif]
[Graphics:../Images/HarvestingModelProof_gr_52.gif]

[Graphics:../Images/HarvestingModelProof_gr_53.gif]
[Graphics:../Images/HarvestingModelProof_gr_54.gif]

To find the solution with the initial condition  [Graphics:../Images/HarvestingModelProof_gr_55.gif],  proceed as follows.

[Graphics:../Images/HarvestingModelProof_gr_56.gif]



[Graphics:../Images/HarvestingModelProof_gr_57.gif]
[Graphics:../Images/HarvestingModelProof_gr_58.gif]

[Graphics:../Images/HarvestingModelProof_gr_59.gif]
[Graphics:../Images/HarvestingModelProof_gr_60.gif]

[Graphics:../Images/HarvestingModelProof_gr_61.gif]
[Graphics:../Images/HarvestingModelProof_gr_62.gif]

[Graphics:../Images/HarvestingModelProof_gr_63.gif]
[Graphics:../Images/HarvestingModelProof_gr_64.gif]

[Graphics:../Images/HarvestingModelProof_gr_65.gif]
[Graphics:../Images/HarvestingModelProof_gr_66.gif]
[Graphics:../Images/HarvestingModelProof_gr_67.gif]

[Graphics:../Images/HarvestingModelProof_gr_68.gif]

[Graphics:../Images/HarvestingModelProof_gr_69.gif]

[Graphics:../Images/HarvestingModelProof_gr_70.gif]

Example (i).  Find the solution to the  D. E.  [Graphics:../Images/HarvestingModelProof_gr_71.gif]  using the general solution and compare it with the one found with Mathematica.

Solution (i).

[Graphics:../Images/HarvestingModelProof_gr_72.gif]

[Graphics:../Images/HarvestingModelProof_gr_73.gif]

[Graphics:../Images/HarvestingModelProof_gr_74.gif]

[Graphics:../Images/HarvestingModelProof_gr_75.gif]

[Graphics:../Images/HarvestingModelProof_gr_76.gif]

Now find the solution with the initial condition  [Graphics:../Images/HarvestingModelProof_gr_77.gif].

[Graphics:../Images/HarvestingModelProof_gr_78.gif]

[Graphics:../Images/HarvestingModelProof_gr_79.gif]

[Graphics:../Images/HarvestingModelProof_gr_80.gif]

[Graphics:../Images/HarvestingModelProof_gr_81.gif]

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

(c) John H. Mathews 2004