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Math Help - [SOLVED] Matrices

  1. #1
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    [SOLVED] Matrices



    by using the cofactor expansion method i got det(A) = 14.

    If i change that matrix using row operations into a upper triangular matrix..am i suppose to get the same determinant??? because i detrminant after row operations to be 5.
    Last edited by b00yeah05; January 26th 2008 at 03:48 PM. Reason: changed values
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  2. #2
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    Quote Originally Posted by b00yeah05 View Post


    by using the cofactor expansion method i got det(A) = 14.

    If i change that matrix using row operations into a upper triangular matrix..am i suppose to get the same determinant??? because i got 2.
    There may be change to the determinant for each row op used, depending on the row operation:

    You should know that:

    1. Multiplication of a row by a constant multiplies the determinant by that constant.

    2. Switching two rows changes the sign of the determinant.

    3. Replacing one row by that row + a times another row has no effect on the determinant.

    So you need to look at the row ops you did and make the appropriate changes to the determinant.
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  3. #3
    Senior Member Peritus's Avatar
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    the determinant of A is indeed 14. Here's a useful site, to help you check your answers:

    Matrix calculator
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  4. #4
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    thanks for the help guys..i really appreciate it..but i solved it, it was a silly mistake that i made
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