First Order Linear D. E.'s

 

Preliminaries. We wish to solve the first order linear D. E. with a given I. C.
[Graphics:p2.txtgr1.gif],
the integrating factor is [Graphics:p2.txtgr2.gif].

 

Computer Lab Work.

Example 1. Use Mathematica to solve the first order linear D. E. with the given I. C.
[Graphics:p2.txtgr3.gif]with y(0) = 3.
Plot the solution over the interval [0, 3].

First enter the functions p[x] and q[x] and the initial condition.

[Graphics:p2.txtgr5.gif][Graphics:p2.txtgr4.gif]

Construct the integrating factor.

[Graphics:p2.txtgr5.gif][Graphics:p2.txtgr6.gif]

Construct the general solution.

[Graphics:p2.txtgr5.gif][Graphics:p2.txtgr7.gif]

Solve for the constant c.

[Graphics:p2.txtgr5.gif][Graphics:p2.txtgr8.gif]

Form the particular solution from the general solution.

[Graphics:p2.txtgr5.gif][Graphics:p2.txtgr9.gif]

Verify that this is the correct solution to the D. E.

[Graphics:p2.txtgr5.gif][Graphics:p2.txtgr10.gif]

Verify that it has the correct I. V. and plot the solution.

[Graphics:p2.txtgr5.gif][Graphics:p2.txtgr11.gif]

[Graphics:p2.txtgr5.gif][Graphics:p2.txtgr12.gif]

 

Example 2. Use Mathematica to solve the first order linear D. E. with the given I. C.
[Graphics:p2.txtgr13.gif]with y(0) = 1.
Plot the solution over the interval [0, 3].

First enter the functions p[x] and q[x] and the initial condition.

[Graphics:p2.txtgr5.gif][Graphics:p2.txtgr14.gif]

Construct the integrating factor.

[Graphics:p2.txtgr5.gif][Graphics:p2.txtgr15.gif]

Construct the general solution.

[Graphics:p2.txtgr5.gif][Graphics:p2.txtgr16.gif]

Solve for the constant.

[Graphics:p2.txtgr5.gif][Graphics:p2.txtgr17.gif]

Form the particular solution from the general solution.

[Graphics:p2.txtgr5.gif][Graphics:p2.txtgr18.gif]

Verify that this is the correct solution to the D. E.

[Graphics:p2.txtgr5.gif][Graphics:p2.txtgr19.gif]

Verify that it has the correct I. V. and plot the solution.

[Graphics:p2.txtgr5.gif][Graphics:p2.txtgr20.gif]

[Graphics:p2.txtgr5.gif][Graphics:p2.txtgr21.gif]

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

(c) John H. Mathews, 1998