Differential Equations - Eigenvalues and Eigenfunctions

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SUMMARY

The discussion focuses on solving the differential equation \(x^2y'' + 2xy' + \lambda y = 0\) with boundary conditions \(y(1) = 0\) and \(y(e^2) = 0\). Participants emphasize the need to find eigenvalues and eigenfunctions, with one user expressing confusion over the auxiliary equation and the term "duplicity" versus "multiplicity." The consensus is that \(\lambda\) must exceed \(1/4\) for a non-trivial solution, and the importance of correctly interpreting the differential equation is highlighted.

PREREQUISITES
  • Understanding of differential equations, specifically second-order linear equations.
  • Familiarity with eigenvalues and eigenfunctions in the context of boundary value problems.
  • Knowledge of boundary conditions and their implications on solutions.
  • Experience with auxiliary equations and their role in solving differential equations.
NEXT STEPS
  • Study the method of solving second-order linear differential equations with variable coefficients.
  • Learn about the Sturm-Liouville theory and its application to eigenvalue problems.
  • Explore the concept of boundary value problems and their significance in mathematical physics.
  • Review the process of determining the multiplicity of eigenvalues in differential equations.
USEFUL FOR

Students studying differential equations, mathematicians focusing on eigenvalue problems, and educators seeking to clarify concepts related to boundary value problems in advanced mathematics.

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Homework Statement


Find the eigenvalues and the eigenfunctions for
x^2y"+2xy'+λy = 0 y(1) = 0, y(e^2) = 0


Homework Equations



See problem

The Attempt at a Solution


My book has one paragraph on this that does not help me. I tried using an auxiliary equation and solving for lambda.
I get (m+√λ)^2 a real number with duplicity two. I don't know what to do with this or if this is even the right first step. The SINGLE paragraph on this doesn't explain anything (it's practically a side note)

I would appreciate some guidance. There are two problems like this on the take home quiz and we didn't go over it in class so I am very lost and confused.
Also I've been pounding my head over this with my directionless fury. Help subside my hate!

Thanks for your time everyone!
 
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You mean "multiplicity" 2 ("duplicity" has a completely different meaning!). And, while you say you "get (m+√λ)^2" you don't say what that is supposed to be- particularly since there is no "m" in the problem. Please show how you got that.

(I'm not sure what you mean by "m" but I get nothing like that. It looks to me like \lambda will have to be larger than 1/4 in order to get a non-trivial function that is 0 for two different x values.)
 
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I got it from changing the DE into
m^2 + 2m + λ
I did the "m" thing because in the previous chapters to solve some equations I would solve the associated homogeneous DE and use the value of m to determine the structure of the general solution.
It's the only step I have made and I feel like even that is wrong. I don't know what to do with the initial values or anything...
Thanks for clearing up the duplicity multiplicity thing, you're right :)

My problem is a complete lack of understanding of what I am supposed to do, and my textbook is not helping haha...
 

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