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Description of eigenvector corresponding to each eigenvalue.

  1. Apr 28, 2014 #1
    I have a problem I need to solve. I can't find anything in my book that tells me how to do it. It might be worded differently in the book, but I'm not 100% sure how to solve this.

    1. The problem statement, all variables and given/known data
    Give a description of the eigenvectors corresponding to each eigenvalue.

    3. The attempt at a solution
    The matrix given is A = [1, 3];[-2, 6]

    I have found the characteristic polynomial with the equation p(t)=det(A-tI)
    the answer for that is p(t)=t^2-7t+12=>(t-4)(t-3)
    so the eigenvalues are λ=4 and λ=4

    Now I have to give description of the eigenvectors corresponding to each eigenvalue??
  2. jcsd
  3. Apr 28, 2014 #2


    Staff: Mentor

    I would start by finding the eigenvectors, and then maybe you'll be able to describe them.
  4. Apr 28, 2014 #3
    Ok I have found out that the vectors are (1,1) and (3,2)

    so could a description be like

    x=a(1,1),a≠o and x=a(3,2),a≠o ??
  5. Apr 29, 2014 #4


    Staff: Mentor

    Looks OK except for one thing. The eigenvalues are λ = 4 and λ = 3. Any scalar multiple of <1, 1> is an eigenvector for λ = 4, and any scalar multiple of <3, 2> is an eigenvector for λ = 3.

    I would use different scalars for the two eigenvectors, not a for both of them.
  6. Apr 29, 2014 #5
    Ok it was a typo I had it for 3, but ok I thank I got it now then.

    thank you :)
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