Eigenvector of complex Eigenvalues

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.
 
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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.
 
There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...
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