Differential Equations Method of Flexible guessing

Click For Summary

Homework Help Overview

The problem involves finding a particular solution \( Y_p \) for the differential equation \( 4y'' + 4y' + y = 3xe^x \) using the method of flexible guessing.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • The original poster attempts to use \( y = Ae^x \) as a guess, but questions arise regarding the dependency of \( A \) on \( x \). They explore \( y = Axe^x \) but find it does not yield a valid solution. Another participant suggests trying \( y_p = Aex + Bxex \) as an alternative approach.

Discussion Status

The discussion includes various attempts at guessing the form of the particular solution, with some participants questioning the validity of their assumptions. There is no clear consensus, but suggestions for alternative forms have been provided, indicating a productive exploration of the problem.

Contextual Notes

Participants are navigating the complexities of the method of flexible guessing and are considering different forms for the particular solution based on the equation's structure.

mike1967
Messages
16
Reaction score
0

Homework Statement


Find a particular solution Yp of the given equation. Primes denote deriviate with respect to x
(method of flexible guess)

Homework Equations


4y''+4y'+y=3xe^x



The Attempt at a Solution


when I used y=Ae^x as guess my A depended on x
So y=Axe^x gave me 12A+9Ax=3x
12A=0
9Ax=3x
does not work,
Before I go on to trying y=Ax^2e^x am I doing this right?
 
Physics news on Phys.org
mike1967 said:

Homework Statement


Find a particular solution Yp of the given equation. Primes denote deriviate with respect to x
(method of flexible guess)

Homework Equations


4y''+4y'+y=3xe^x



The Attempt at a Solution


when I used y=Ae^x as guess my A depended on x
I don't know what you mean by "my A depended on x." A is a constant, so is not dependent on any variable.
mike1967 said:
So y=Axe^x gave me 12A+9Ax=3x
12A=0
9Ax=3x
does not work,
Before I go on to trying y=Ax^2e^x am I doing this right?
Why don't you try yp = Aex + Bxex?
 
Yp=3/9xe^x-4/9e^x right?
 
mike1967 said:
Yp=3/9xe^x-4/9e^x right?

Right.
 
mike1967 said:
Yp=3/9xe^x-4/9e^x right?
This is something you should get in the habit of checking for yourself. You've already done all the hard work. If 4yp'' + 4y' + yp [itex]\equiv[/itex] 3xex, then your solution is correct.
 

Similar threads

Replies
7
Views
2K
Replies
10
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K
Replies
9
Views
3K
Replies
7
Views
2K
Replies
3
Views
2K
Replies
9
Views
3K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 2 ·
Replies
2
Views
1K