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Homework Help: Confused on finding Eigenvalues and Eigenvectors

  1. Oct 23, 2005 #1
    confused on finding Eigenvalues and Eigenvectors!!

    hello everyone, i can't understand this example, how did they find the Eigen value of 3?! Aslo an Eigen vector of 1 1? http://img438.imageshack.us/img438/1466/lastscan1oc.jpg [Broken]
    Last edited by a moderator: May 2, 2017
  2. jcsd
  3. Oct 23, 2005 #2
    See http://mathworld.wolfram.com/CharacteristicEquation.html" [Broken].
    Last edited by a moderator: May 2, 2017
  4. Oct 23, 2005 #3
    thanks, i did that and I didn't get the right answer, look when i try to solve...
    http://img442.imageshack.us/img442/4810/lastscan1fp.jpg [Broken]
    Last edited by a moderator: May 2, 2017
  5. Oct 23, 2005 #4
    You've factored it incorrectly.
  6. Oct 23, 2005 #5
    i know, i can't factor that and get a nice number, i'd have to use the quadtract equation, but that can't be right because the book got a nice answer of 3.
  7. Oct 23, 2005 #6


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    Homework Helper

    As Muzza said, only the factoring was wrong!

    [tex]\lambda ^2 - 4\lambda + 3 = \left( {\lambda - 1} \right)\left( {\lambda - 3} \right) \ne \left( {\lambda - 4} \right)\left( {\lambda + 1} \right)[/tex]
  8. Oct 23, 2005 #7
    ohhh wow i suck hah, thank u so much!! why did they only use [tex]\lambda = 3[/tex] when it can also equal 1?
  9. Oct 23, 2005 #8


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    Science Advisor

    Even knowing that one solution was 3, so one factor must be x- 3 you couldn't factor it??

    Read it carefully! It specifically says "an eigenvalue", not the eigenvalue. And immediately below states that there is another and solves for it.
  10. Oct 23, 2005 #9
    This is what we witnessed today. :surprised
    To think i have a 3.77 GPA. What is the world coming too?
    Anywho, thanks for the explanation everyone.
    Last edited: Oct 23, 2005
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