Eigenvalues of a 3x3 Matrix

In summary, eigenvalues of a 3x3 matrix are special numbers that represent the scaling factor of the eigenvectors when the matrix is multiplied by them. To find the eigenvalues, one needs to solve the characteristic polynomial equation. Eigenvalues are important in linear algebra as they provide information about the behavior of a matrix and its associated linear transformation. They are closely related to eigenvectors, which represent the direction of the transformation, while eigenvalues represent the magnitude. A 3x3 matrix can have complex eigenvalues, which are still valid in understanding the matrix's behavior.
  • #1
Jalo
120
0

Homework Statement


Given the matrix A=

1 -1 -1
-1 1 -1
-1 -1 1

Find the eigenvalues.

Homework Equations



I = identity matrix

The Attempt at a Solution



det(A-xI) = (1-x)3 - 2 - 3*(1-x) = 0 ⇔
⇔(1-x)3 - 3*(1-x) - 2 = 0

I can't find a way to solve this equation...
Any help would be appreciated!4

Daniel
 
Last edited by a moderator:
Physics news on Phys.org
  • #2
If you let y=1-x, then the cubic [itex]y^3-3y-2[/itex] has a zero at y=2.
 

1. What are eigenvalues of a 3x3 matrix?

Eigenvalues of a 3x3 matrix are the special set of numbers that represent the scaling factor of the eigenvectors when the matrix is multiplied by them. In other words, they are the values that do not change the direction of the eigenvectors when the matrix is applied to them.

2. How do I find the eigenvalues of a 3x3 matrix?

To find the eigenvalues of a 3x3 matrix, you need to solve the characteristic polynomial equation det(A-λI)=0, where A is the matrix and λ is the eigenvalue. This will give you three possible eigenvalues for the matrix.

3. Why are eigenvalues important in linear algebra?

Eigenvalues are important in linear algebra because they provide information about the behavior of a matrix and its associated linear transformation. They can help determine whether a matrix is invertible, diagonalizable, or has a unique solution to a system of linear equations.

4. What is the relationship between eigenvalues and eigenvectors?

Eigenvalues and eigenvectors are closely related. Eigenvectors are the vectors that do not change direction when multiplied by the matrix, and eigenvalues are the corresponding scalar values that scale the eigenvectors. In other words, the eigenvectors represent the direction and the eigenvalues represent the magnitude of the transformation.

5. Can a 3x3 matrix have complex eigenvalues?

Yes, a 3x3 matrix can have complex eigenvalues. Complex eigenvalues occur when the characteristic polynomial equation has complex roots. These eigenvalues are still valid and important in understanding the behavior of the matrix and its linear transformation.

Similar threads

  • Calculus and Beyond Homework Help
Replies
2
Views
381
  • Calculus and Beyond Homework Help
Replies
2
Views
521
  • Calculus and Beyond Homework Help
Replies
7
Views
1K
  • Calculus and Beyond Homework Help
Replies
8
Views
1K
  • Calculus and Beyond Homework Help
Replies
5
Views
518
  • Calculus and Beyond Homework Help
Replies
8
Views
2K
  • Calculus and Beyond Homework Help
Replies
25
Views
2K
  • Calculus and Beyond Homework Help
Replies
3
Views
567
  • Calculus and Beyond Homework Help
Replies
3
Views
324
  • Calculus and Beyond Homework Help
Replies
4
Views
831
Back
Top