Do Invertible Matrices Influence the Equality of Characteristic Polynomials?

  • Thread starter talolard
  • Start date
  • Tags
    Polynomial
In summary, characteristic polynomials are mathematical expressions that are used to find the roots of a given matrix or linear transformation. They are calculated by taking the determinant of the matrix minus a variable, and setting it equal to zero. The roots of the characteristic polynomial are known as eigenvalues, and they are important in determining the behavior of a system or matrix. Characteristic polynomials are a fundamental concept in linear algebra and are widely used in various fields such as physics, engineering, and computer science. They provide a powerful tool for analyzing and solving problems involving matrices and linear transformations.
  • #1
talolard
125
0

Homework Statement


Let A and B be to nXn matrices and A is invertible. Prove: [tex] P_{AB}(x)=P_{BA}(x) [/tex]


The Attempt at a Solution


Since A is invertible we have det(A)=0. [tex]det(AB)= det(A)det(B)=0det(B)=0 ->P_{AB}(x)=P_{BA}(x)=0 [/tex]

Is that correct?




[
 
Physics news on Phys.org
  • #2
netheril96, you are supposed to give hints and help. Not work out people's problems for them. Read the forum guidelines.
 
  • #3
Dick said:
netheril96, you are supposed to give hints and help. Not work out people's problems for them. Read the forum guidelines.

But this problem is so easy that the only hint I can give is the direct answer
 
  • #4
talolard said:

Homework Statement


Let A and B be to nXn matrices and A is invertible. Prove: [tex] P_{AB}(x)=P_{BA}(x) [/tex]

The Attempt at a Solution


Since A is invertible we have det(A)=0. [tex]det(AB)= det(A)det(B)=0det(B)=0 ->P_{AB}(x)=P_{BA}(x)=0 [/tex]

Is that correct?

[

Talolard, the determinants you've written down are all just numbers. They don't have anything to do with the characteristic polynomial. What's the definition of a characteristic polynomial in terms of a determinant? Besides if A is invertible it's determinant is NOT 0.
 
  • #5
netheril96 said:
But this problem is so easy that the only hint I can give is the direct answer

It's not 'so easy' for a lot of people. If the only hint you can think of is to give the solution, don't. Find another thread to work on. Could you remove the post with your proof in it please?
 
  • #6
Dick said:
It's not 'so easy' for a lot of people. If the only hint you can think of is to give the solution, don't. Find another thread to work on. Could you remove the post with your proof in it please?

Deleted
 
  • #7
netheril96 said:
Deleted

Thanks!
 
  • #8
You may wish to consider similar matrices here
 

Related to Do Invertible Matrices Influence the Equality of Characteristic Polynomials?

What is a characteristic polynomial?

A characteristic polynomial is a polynomial function that is used to find the eigenvalues of a square matrix. It is typically denoted by det(A-λI), where A is the matrix and λ is the variable.

How is a characteristic polynomial used in mathematics?

A characteristic polynomial is used in linear algebra to find the eigenvalues of a matrix, which are important in understanding the behavior of a system. It is also used in differential equations to solve for the general solutions.

What is the degree of a characteristic polynomial?

The degree of a characteristic polynomial is equal to the size of the matrix, or the number of rows/columns. For a 3x3 matrix, the characteristic polynomial will have a degree of 3.

Can a characteristic polynomial have complex roots?

Yes, a characteristic polynomial can have complex roots. This is because the eigenvalues of a matrix can be complex numbers, and the characteristic polynomial is used to find these eigenvalues.

Why is the characteristic polynomial important in understanding systems?

The characteristic polynomial is important because it helps determine the stability and behavior of a system. The eigenvalues of a matrix found using the characteristic polynomial can indicate whether the system will converge or diverge, and how quickly it will do so.

Similar threads

  • Calculus and Beyond Homework Help
Replies
4
Views
4K
  • Calculus and Beyond Homework Help
Replies
25
Views
2K
  • Calculus and Beyond Homework Help
Replies
28
Views
4K
  • Calculus and Beyond Homework Help
Replies
14
Views
5K
  • Calculus and Beyond Homework Help
Replies
15
Views
2K
  • Calculus and Beyond Homework Help
Replies
17
Views
1K
  • Calculus and Beyond Homework Help
Replies
6
Views
2K
  • Calculus and Beyond Homework Help
Replies
4
Views
5K
  • Calculus and Beyond Homework Help
Replies
5
Views
4K
  • Calculus and Beyond Homework Help
Replies
7
Views
2K
Back
Top