Matrix, eigenvalues and diagonalization

In summary, the conversation discusses how to prove that a matrix is not able to be diagonalized, even though it has eigenvalues of k=3 and k=-1. It is mentioned that -1 is a double eigenvalue, meaning that the matrix may not have two independent eigenvectors corresponding to that eigenvalue. The solution is to plug in -1 and show that there is only one independent solution, proving that the matrix cannot be diagonalized.
  • #1
jkeatin
66
0
Matrix A= 1 2 0
2 1 0
2 -1 3



i got eigenvalues k=3 k=-1 what do i do after that to prove it is not able to be diagonalized
 
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  • #3
jkeatin said:
i got eigenvalues k=3 k=-1 what do i do after that to prove it is not able to be diagonalized

Hi jkeatin! :smile:

-1 is a is a double eigenvalue …

so just plug -1 in and solve, and show that there is only one independent solution. :wink:
 
  • #4


The point is that an n by n matrix is diagonalizable if and only if it has n independent eigenvectors. Since -1 is a double root of the characteristic polynomial, the matrix may not have two independent eigenvectors corresponding to eigenvalue -1. That is what you need to prove.
 
  • #5


thanks guys, got it!
 

Related to Matrix, eigenvalues and diagonalization

1. What is a matrix?

A matrix is a rectangular array of numbers or symbols that is arranged in rows and columns. It can be used to represent and manipulate linear equations, transformations, and other mathematical operations.

2. What are eigenvalues and eigenvectors?

Eigenvalues and eigenvectors are concepts in linear algebra that are used to describe the behavior of a linear transformation. Eigenvalues are the values that, when multiplied by the eigenvectors, give back the same vector but with a different scale factor. In other words, they represent the amount by which the eigenvectors are scaled when they are transformed by the matrix. Eigenvectors are the special vectors that remain in the same direction after being transformed by the matrix.

3. Why is diagonalization important?

Diagonalization is an important concept in linear algebra because it allows us to simplify the calculation of certain operations on matrices, such as powers and determinants. It also helps us to better understand the behavior of linear transformations and systems of linear equations.

4. How do you find the eigenvalues and eigenvectors of a matrix?

To find the eigenvalues and eigenvectors of a matrix, we first need to find the roots of the characteristic polynomial of the matrix. The eigenvalues are the solutions to this polynomial, and the corresponding eigenvectors can be found by solving a system of equations using the eigenvalues. There are also various algorithms and methods that can be used to find the eigenvalues and eigenvectors of a matrix.

5. Can every matrix be diagonalized?

No, not every matrix can be diagonalized. A matrix can only be diagonalized if it has a full set of linearly independent eigenvectors. In other words, if the matrix is not invertible, it cannot be diagonalized. Additionally, some matrices may have repeated eigenvalues, making them non-diagonalizable.

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