Solving Eigenvector Problems: A+B and AB with Corresponding Eigenvalues

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In summary, if v is an eigenvector of both A and B with corresponding eigenvalues lambda and mui respectively, then v is also an eigenvector of A+B with corresponding eigenvalue (lambda + mui), and of AB with corresponding eigenvalue lambda*mui.
  • #1
Jennifer1990
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Homework Statement


Suppose that v is an eigenvector of both A and B with corresponding eigenvalues lambda and mui respectively. Show that v is an eigenvector of A+B and of AB and determine the corresponding eigenvalues


Homework Equations





The Attempt at a Solution


Av = lambda*v
Bv = mui*v
this is all i can think of...can someone give me a hint abt the next step?
 
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  • #2


Add the two equations together, tada! Of course, you'll need to exploit associativity... or linearity... man I am always getting terms confused.
 
Last edited:
  • #3


u mean like:
(Av +Bv) = lambda*v + mui*v
(A+B)v = (lambda + mui) v
 
  • #4


Yup! As for finding the eigenvalues of AB, simply multiply AB by v and remember that your eigenvalues are scalars that can move freely.
 

1. What is an eigenvector?

An eigenvector is a vector that does not change its direction when multiplied by a given matrix. It only changes in magnitude by a scalar factor, known as the eigenvalue.

2. How is an eigenvector used in a math problem?

In a math problem, eigenvectors are used to simplify complex calculations involving matrices. They can also be used to find the principal components of a system or to identify patterns in data.

3. What are the applications of eigenvectors in science and technology?

Eigenvectors have many applications in science and technology, including image and signal processing, quantum mechanics, computer graphics, and machine learning. They are also used in engineering for structural analysis and control systems.

4. Can you provide an example of an eigenvector math problem?

Sure, here's an example: Given a matrix A = [3 2; 2 1], find the eigenvectors and eigenvalues of A. The eigenvectors will be the solution to the equation Ax = λx, where λ is the eigenvalue. The resulting eigenvectors are [1, -1] and [2, 1], with corresponding eigenvalues of 4 and 0.

5. Are there any limitations or challenges when working with eigenvector math problems?

One limitation of eigenvectors is that they may not exist for every matrix. Additionally, finding eigenvectors and eigenvalues can be computationally intensive, especially for larger matrices. Finally, understanding the geometric interpretation of eigenvectors can be challenging for some individuals.

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