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Determinant of 5x5 matrix

  1. Oct 21, 2009 #1
    1. The problem statement, all variables and given/known data
    so my problem is to calculate the determinant of this matrix
    [tex]\left[\begin{array}{ccccc}
    1 & 2 & 3 & 3 & 5 \\
    3 & 2 & 1 & 2 & 2 \\
    1 & 2 & 3 & 4 & 5 \\
    -1 & 0 & -8 & 1 & 2 \\
    7 & 2 & 1 & 3 & 2
    \end{array}\right][/tex]



    2. Relevant equations



    3. The attempt at a solution
    my calculation -> http://img29.imageshack.us/img29/1120/21102009124.th.jpg [Broken]
    i know to use Laplace, but my teacher said me "at first you should reduce matrix to 3x3 or even 2x2 - it's easier to calculate the determinant"
    but i don't understand this methode at all.
    i've done this problem and my solution is -379 and i know it's wrong (correct is -224)
    please help.
     
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Oct 21, 2009 #2
    The third line of your second determinant is incorrect.
     
  4. Oct 21, 2009 #3
    Last edited by a moderator: May 4, 2017
  5. Oct 21, 2009 #4
    Your last determinant should be

    [tex]\left|\begin{array}{cc} -18 & 1\\ -50 &9\end{array}\right|[/tex]

    not

    [tex]\left|\begin{array}{cc} -18 & 0\\ -50 &9\end{array}\right|[/tex]
     
  6. Oct 21, 2009 #5
    yeah, my bad
    but thanks now it's correct
    thanks a lot :)
     
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