Is Lambda an Eigenvalue of A in the Cayley-Hamilton Theorem Proof?

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SUMMARY

The discussion centers on the Cayley-Hamilton Theorem and the conditions under which a scalar lambda can be considered an eigenvalue of a matrix A. It is established that lambda is an eigenvalue of A if and only if the matrix expression lambda * I - A is not invertible. The confusion arises from the interpretation of the proof, where it is clarified that the invertibility of lambda * I - A does not imply that lambda is an eigenvalue, but rather the opposite. The participants emphasize the importance of understanding the definitions and implications of eigenvalues in the context of linear algebra.

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  • Understanding of eigenvalues and eigenvectors in linear algebra
  • Familiarity with the Cayley-Hamilton Theorem
  • Knowledge of matrix invertibility and determinants
  • Basic concepts of linear transformations and matrix operations
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Students and professionals in mathematics, particularly those studying linear algebra, as well as educators looking to clarify the concepts of eigenvalues and the Cayley-Hamilton Theorem.

vabamyyr
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i met a proof to cayley hamilton theorem and have some questions.

It uses that lambda*I - A is invertible. But lambda is surely an eigenvalue of A and 1/(lamda*I - A) is not legit so how is it legal to use that.
 
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Writing 1/(lambda*I-A) is also not allowed.

Why is lambda an eigenvalue? Who says so? It is just a greek letter, probably representing some scalar. As it is unles you post all of the proof who can possibly say whether it is correct or not.
 
http://www.math.chalmers.se/~wennberg/Undervisning/ODE/linalg.pdf
 
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Also I have some questions on these topics
 

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The first sentence of the proof specifically states that "if lambda is not an eigenvalue of A"...
 
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I don't know about cayley-hamilton but I do know that lambda is an eigenvalue of A iff lambda * I - A is NOT invertible.
 
Hmm? What do you mean by that (in regards to this post)?
 
Ah, I misinterpreted his post. At first reading I thought he was claiming that lambda * I - A is invertible meant that lambda was an eigenvalue of A. Now I see that he was claiming lambda was an eigenvalue of A separately from that statement.
 

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