Results 1 to 5 of 5

Math Help - Matrices - eigenvalues

  1. #1
    Junior Member
    Joined
    May 2010
    Posts
    27

    Matrices - eigenvalues

    I have a question here relating to getting the eigenvalues of a matrix.
    The matrix is 3 x 3. Im just wondering that when you are getting the determinant of
    det(I*Lambda - A). Is it ok to row reduce the matrix A first before subbing into this equation?
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Math Engineering Student
    Krizalid's Avatar
    Joined
    Mar 2007
    From
    Santiago, Chile
    Posts
    3,654
    Thanks
    14
    no because for any elementary row operation you want to do, doesn't matter when reducing the matrix into the echelon form, but it does affect the determinant, so it needs to be computed the determinant given the "intact" matrix.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    MHF Contributor
    Joined
    Mar 2010
    From
    Florida
    Posts
    3,093
    Thanks
    5
    Quote Originally Posted by frog View Post
    I have a question here relating to getting the eigenvalues of a matrix.
    The matrix is 3 x 3. Im just wondering that when you are getting the determinant of
    det(I*Lambda - A). Is it ok to row reduce the matrix A first before subbing into this equation?
    No. If your matrix reduces to the identity matrix, then the eigenvalues will all be 1 when in fact the eigenvalues maybe be 2,3,-2,....
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Junior Member
    Joined
    May 2010
    Posts
    27
    Cool..(forgot you could completely reduce it to the the identity!)
    Follow Math Help Forum on Facebook and Google+

  5. #5
    MHF Contributor
    Joined
    Mar 2010
    From
    Florida
    Posts
    3,093
    Thanks
    5
    Quote Originally Posted by frog View Post
    Cool..(forgot you could completely reduce it to the the identity!)
    Singular matrices don't reduce to the identity. That was just my example since it would be easy to understand.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. [SOLVED] Eigenvalues and Matrices
    Posted in the Algebra Forum
    Replies: 9
    Last Post: August 30th 2010, 01:08 PM
  2. Eigenvalues of Orthogonal Matrices
    Posted in the Advanced Algebra Forum
    Replies: 7
    Last Post: November 28th 2009, 12:26 PM
  3. similar matrices and eigenvalues
    Posted in the Advanced Algebra Forum
    Replies: 1
    Last Post: November 7th 2009, 04:49 PM
  4. Matrices and eigenvalues
    Posted in the Advanced Algebra Forum
    Replies: 1
    Last Post: October 31st 2009, 08:00 AM
  5. Finding all 2 by 2 matrices that have eigenvalues x and y
    Posted in the Advanced Algebra Forum
    Replies: 1
    Last Post: April 5th 2009, 05:46 PM

Search Tags


/mathhelpforum @mathhelpforum