Finding Eigenvalues of an Arbitrary Matrix

In summary, the conversation discusses finding the eigenvalues of a matrix C=(A-alpha*I) and proving that lambda is an eigenvalue of A only if (lambda-alpha) is an eigenvalue of C. The method for finding eigenvalues is through solving the equation det(M-xI)=0, where M is any square matrix. It is also mentioned that if C-tI is not invertible, then A-(alpha+t)I is also not invertible.
  • #1
himurakenshin
21
0
How can i find the eigen value(s) of A - (alpha)I
where A is an arbitrary matrix ?
 
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  • #2
Your question is ambiguous. Do you mean just find the eigenvalues of A- which would mean solving the equation det(A- alpha*I)= 0 for alpha or do you mean specifically finding eigenvalues of A- alpha*I for a given value of I?
 
  • #3
sorry, where I is the identity matrix.
the matrix is C=(A-alpha*I)
I need to find the eigen values of C
 
  • #4
the eigenvalues of any square matrix, call it M, are the roots of the polynomial in x

det(M-xI)

although if you know the eigen values of A you know them of C too.
 
  • #5
matt grime said:
the eigenvalues of any square matrix, call it M, are the roots of the polynomial in x

det(M-xI)
yes I know this, but I don't know how to find the eigen value of that paticular matrix (A can be any matrix). The actual question is that I have to prove that lambda is an eigen value of A only if (lamda - alpha) is an eigen value of C
 
  • #6
well, that wasn't waht you asked was it?

t is an eigenvalue of M if and only if M-tI is not invertible.

let a be alpha
If C-tI=A-aI-tI is not invertible, then A-(a+t)I is not invertible, can you fill in the blanks?
 
  • #7
got it. thanks a lot :)
 

1. What is an eigenvalue?

An eigenvalue is a scalar value that represents how a matrix will act on a vector. It is often denoted by the Greek letter lambda (λ) and is a key concept in linear algebra.

2. Why is finding eigenvalues important?

Finding eigenvalues allows us to understand the behavior of a matrix and its associated linear transformation. It also helps in solving systems of linear equations and in many other applications, such as data compression and machine learning.

3. How do you find eigenvalues of an arbitrary matrix?

To find the eigenvalues of an arbitrary matrix, we need to solve the characteristic equation, which is the determinant of the matrix minus a scalar multiplied by the identity matrix. This equation will have roots that represent the eigenvalues of the matrix.

4. Can all matrices have eigenvalues?

No, not all matrices have eigenvalues. A matrix must be square (same number of rows and columns) to have eigenvalues. Additionally, a matrix must also be invertible (have a non-zero determinant) to have eigenvalues.

5. How are eigenvalues and eigenvectors related?

Eigenvalues and eigenvectors are closely related. Eigenvectors are the vectors that are transformed only by a scaling factor when multiplied by a matrix, and the corresponding eigenvalues represent the magnitude of the scaling factor. In other words, eigenvectors are the directions along which a matrix acts only by stretching or shrinking, and eigenvalues are the amount by which it stretches or shrinks those eigenvectors.

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