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Homework Help: LU Decomposition

  1. Oct 22, 2007 #1
    1. The problem statement, all variables and given/known data
    A = [tex]
    \left| \begin{array}{ccc}
    2 & 0 & 4 \\
    0 & 4 & -8 \\
    3 & -1 & 2 \end{array} \right|.\]
    [/tex]

    Find the LU decomposition.

    3. The attempt at a solution
    My question is why do you need to interchange rows 3 & 1 at the start of the problem? My initial attempt was to find the upper matrix using the format as given. I got
    U = [tex]
    \left| \begin{array}{ccc}
    2 & 0 & 4 \\
    0 & 4 & -8 \\
    0 & 0 & -6 \end{array} \right|.\]
    [/tex]

    doesn't that satisfy the requirements for an U matrix?

    According to the calculator I'm using the U matrix should be
    [tex]
    \left| \begin{array}{ccc}
    3 & -1 & 2 \\
    0 & 4 & -8 \\
    0 & 0 & 4 \end{array} \right|.\]
    [/tex]
     
  2. jcsd
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