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Math Help - LU Decompistion

  1. #1
    Newbie
    Joined
    Feb 2008
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    4

    LU Decompistion

    Hello, I have lookd and looked and cannot figure this problem out. Can anyone help please?

    Show that the following A matrix is invertible but has no LU Decomposition.
    A = [01]
    [10]
    Explain.

    Help!
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  2. #2
    Member
    Joined
    Dec 2007
    Posts
    131
    It is invertible because its determinant is not 0. An invertible matrix has an LU decomposition if it's cofactors are all non zero.

    However, when you look at the cofactors, you should see a problem.

    edit: the more i think about this, the more i ask myself "what are the cofactors of a simple 2x2 matrix?" would they not be just the elements themselves? anyone?
    Last edited by xifentoozlerix; February 21st 2008 at 03:22 PM. Reason: unsure
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