Eigenvector of complex Eigenvalues

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Homework Help Overview

The discussion revolves around finding the eigenvectors corresponding to complex eigenvalues of a given 2x2 matrix. Participants are exploring the implications of complex eigenvalues and the process of determining the associated eigenvectors.

Discussion Character

  • Mixed

Approaches and Questions Raised

  • Participants discuss the calculation of eigenvalues and the subsequent steps to find the eigenvectors. There are attempts to substitute the eigenvalues back into the matrix equation, leading to questions about the resulting expressions and how to simplify them. Some participants express confusion about the calculations and seek clarification on the process.

Discussion Status

Several participants have shared their attempts and calculations, with some providing partial solutions. There is an ongoing exploration of the calculations involved in finding the eigenvectors, and some participants have noted discrepancies in their results, prompting further discussion.

Contextual Notes

Participants mention the complexity of the problems in this section and express concerns about the difficulty level in relation to an upcoming test. There is a sense of shared struggle with the calculations involved in the problem.

bowlbase
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Homework Statement


##A=\begin{bmatrix} 16 &{-6}\\39 &{-14} \end{bmatrix}##



Homework Equations





The Attempt at a Solution



I did ##A=\begin{bmatrix} 16-\lambda &{-6}\\39 &{-14-\lambda} \end{bmatrix}##

and got that ##\lambda_1=1+3i## and ##\lambda_2=1-3i##

The solution is partially given for both the vectors:

##x_1=\begin{bmatrix} 1+i \\ ?+?i\end{bmatrix}##
I should fill in the "?". I tried placing 1+3i into replace lambda:

##\begin{bmatrix} 16-(1+3i) &{-6}\\39 &{-14-(1+3i) } \end{bmatrix}##
Which I then get:
##\begin{bmatrix} 15-3i &{-6}\\39 &{-15-3i } \end{bmatrix}##


I don't know what to do from here. I've tried all sorts of ways to get this figured out but I just keep getting the wrong answers.
 
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bowlbase said:

Homework Statement


##A=\begin{bmatrix} 16 &{-6}\\39 &{-14} \end{bmatrix}##

Homework Equations


The Attempt at a Solution



I did ##A=\begin{bmatrix} 16-\lambda &{-6}\\39 &{-14-\lambda} \end{bmatrix}##

and got that ##\lambda_1=1+3i## and ##\lambda_2=1-3i##

The solution is partially given for both the vectors:

##x_1=\begin{bmatrix} 1+i \\ ?+?i\end{bmatrix}##
I should fill in the "?". I tried placing 1+3i into replace lambda:

##\begin{bmatrix} 16-(1+3i) &{-6}\\39 &{-14-(1+3i) } \end{bmatrix}##
Which I then get:
##\begin{bmatrix} 15-3i &{-6}\\39 &{-15-3i } \end{bmatrix}##I don't know what to do from here. I've tried all sorts of ways to get this figured out but I just keep getting the wrong answers.
Add -39 times the first row to 15 - 3i times the second row. That should result in the second row being all zeros. This seems to be a pretty messy problem to do by hand.
 
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For whatever reason all of the problems for this section are like this. I just hope our test tomorrow is simpler...

Got ahead of myself on posting. 1 sec while I do what you said.

They did cancel so I'm left with

##(-585+117i)x_1=-234x_2##

##x_1=1+i=\frac{-234x_2}{-585+117i}##

which is ##x_2(\frac{135}{338}+\frac{27i}{338})=1+i##

so ##x_2=\frac{26}{9}+\frac{52i}{27}##

I got it wrong somewhere.
 
Last edited:
I figure it out:

##(-585+117i)x_1+234x_2=0## where ##x_1=1+i##

##\frac{(-585+117i)(1+i)}{-234}=x_2##

##x_2=3+2i##

This is really exactly the same so I'm not sure what happened up there. Probably just calculations. I used my calculator once I had it in the second equation form.
 

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