## Homework 3, due September 15, 2011.

Due at noon on Thursday, September 15, 2011.
goodwine
Site Admin
Posts: 1596
Joined: Tue Aug 24, 2004 4:54 pm
Location: 376 Fitzpatrick
Contact:

### Homework 3, due September 15, 2011.

Reading: Chapter 3.

Exercises: 2.9, 2.10 (9, 10 and 11 only), 2.14, 2.19, 2.21, 2.22 and 2.25 (2, 4, 6 and 8 only).
Bill Goodwine, 376 Fitzpatrick
Jessie

### Re: Homework 3, due September 15, 2011.

For linear first order differential non homogeneous equations with variable coefficients are there two different methods that you can use to find the general solution? (Problem 2.21) I know that you can use variation of parameters but undetermined coefficients does not work. Thanks
goodwine
Site Admin
Posts: 1596
Joined: Tue Aug 24, 2004 4:54 pm
Location: 376 Fitzpatrick
Contact:

### Re: Homework 3, due September 15, 2011.

Jessie wrote:For linear first order differential non homogeneous equations with variable coefficients are there two different methods that you can use to find the general solution? (Problem 2.21) I know that you can use variation of parameters but undetermined coefficients does not work. Thanks
The methods for nonlinear first order (separable or exact) may work even though the equation is linear.
Bill Goodwine, 376 Fitzpatrick
sschwane

### Re: Homework 3, due September 15, 2011.

Jessie wrote:For linear first order differential non homogeneous equations with variable coefficients are there two different methods that you can use to find the general solution? (Problem 2.21) I know that you can use variation of parameters but undetermined coefficients does not work. Thanks
I thought the same thing at first, but undetermined coefficients will work if you get the original equation in the right form before you start it.
goodwine
Site Admin
Posts: 1596
Joined: Tue Aug 24, 2004 4:54 pm
Location: 376 Fitzpatrick
Contact:

### Re: Homework 3, due September 15, 2011.

sschwane wrote:
Jessie wrote:For linear first order differential non homogeneous equations with variable coefficients are there two different methods that you can use to find the general solution? (Problem 2.21) I know that you can use variation of parameters but undetermined coefficients does not work. Thanks
I thought the same thing at first, but undetermined coefficients will work if you get the original equation in the right form before you start it.
I don't see how you can convert it to a constant coefficient equation so that undetermined coefficients works, so in general that will not be a viable approach for this type of equation. However, there is no point in being too formalistic, and if you found a way that gives the right solution, then it's ok.
Bill Goodwine, 376 Fitzpatrick