Finding Eigenvectors with a Parameter in Homework Solution?

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SUMMARY

The discussion centers on finding eigenvalues and eigenvectors for a 3x3 matrix A, where all entries are equal to 1. The eigenvalues identified are 0 and 3, consistent with the lecturer's findings. The confusion arises in the representation of eigenvectors; while textbooks typically express them in terms of a parameter, the lecturer provided specific coordinate values. The solution involves recognizing that any scalar multiple of an eigenvector is also an eigenvector, leading to a parametrized form that encompasses all multiples.

PREREQUISITES
  • Understanding of eigenvalues and eigenvectors
  • Familiarity with matrix operations, specifically determinants
  • Knowledge of linear algebra concepts, particularly scalar multiplication
  • Ability to work with parametrized equations in vector spaces
NEXT STEPS
  • Study the derivation of eigenvalues using the characteristic polynomial
  • Learn how to express eigenvectors in parametrized forms
  • Explore the implications of scalar multiplication on eigenvectors
  • Investigate the geometric interpretation of eigenvalues and eigenvectors
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Students studying linear algebra, educators teaching eigenvalue problems, and anyone seeking to clarify the representation of eigenvectors in mathematical contexts.

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Homework Statement




Okay, we've got a 3x3 matrix. All the entries are equal to 1. Call the matrix A.
Basically It looks like this
1 1 1
1 1 1
1 1 1

find all the eigenvalues and eigenvectors.

The Attempt at a Solution



Right, I got the eigenvalues being 0 and 3, the same as my lecturer got. That's fine, I just let the determinant of (\lambdaI-A) equal 0.
When getting the eigenvectors, every book I read gives the vector in terms of a parameter, such as t. However, my lecturer got vectors with specific coordinates.

What am I supposed to do?
 
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Maybe_Memorie said:

Homework Statement




Okay, we've got a 3x3 matrix. All the entries are equal to 1. Call the matrix A.
Basically It looks like this
1 1 1
1 1 1
1 1 1

find all the eigenvalues and eigenvectors.

The Attempt at a Solution



Right, I got the eigenvalues being 0 and 3, the same as my lecturer got. That's fine, I just let the determinant of (\lambdaI-A) equal 0.
When getting the eigenvectors, every book I read gives the vector in terms of a parameter, such as t. However, my lecturer got vectors with specific coordinates.

What am I supposed to do?

Let v be an eigenvector of your matrix and let l be its eigenvalue. If A is your matrix then, as you know Av = lv. Now, what if you were to take a multiple of v, is that an eigenvector? That is, if k is a scalar, is kv an eigenvector? If so, can you think of a parametrized form of v that would include all multiples of v?
 

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