Results 1 to 3 of 3

Math Help - Find the inverse of 3X3 matrix (mod 19)

  1. #1
    Newbie
    Joined
    Nov 2012
    From
    singapore
    Posts
    5

    Find the inverse of 3X3 matrix (mod 19)

    I have been trying to find the inverse matrix of the following matrix (mod 19)

     A = \begin{bmatrix} 1 & 14 & 9 \\ 7 & 15 & 8 \\ 2 & 13 & 4\end{bmatrix} mod 19. .

    I used gauss-jordan elimination method (i.e. augment A with identity matrix, and reduce the left matrix to an identity matrix) and its very tedious. Everytime i change an element, another element of the same row gets affected then i have to go back and redo all over.

    Is there an efficent way to do this? Thanks in advance for your help.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    Joined
    Sep 2012
    From
    Australia
    Posts
    3,619
    Thanks
    592

    Re: Find the inverse of 3X3 matrix (mod 19)

    Hey ScorpFire.

    Take a look at this:

    Finite Fields Calculations - Newsreader - MATLAB Central
    Follow Math Help Forum on Facebook and Google+

  3. #3
    MHF Contributor

    Joined
    Mar 2011
    From
    Tejas
    Posts
    3,380
    Thanks
    746

    Re: Find the inverse of 3X3 matrix (mod 19)

    you shouldn't have to "start all over".

    i recommend gauss-jordan (row-reduction) in this order:

    12R1 + R2
    8R2
    17R1 + R3
    5R2 + R1
    6R2 + R3
    16R3
    3R3 + R2
    6R3 + R2 <---you should be done at this point.

    remember to reduce mod 19 after each step (to keep the numbers you're working with small).
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Find the inverse of a matrix
    Posted in the Advanced Algebra Forum
    Replies: 3
    Last Post: December 29th 2009, 12:18 AM
  2. how can i find the inverse of matrix?
    Posted in the Advanced Algebra Forum
    Replies: 6
    Last Post: June 2nd 2009, 11:54 AM
  3. Find the inverse of a matrix
    Posted in the Advanced Algebra Forum
    Replies: 4
    Last Post: May 17th 2009, 10:19 AM
  4. Replies: 1
    Last Post: February 10th 2009, 01:54 PM
  5. How to find inverse of matrix?
    Posted in the Calculators Forum
    Replies: 4
    Last Post: October 26th 2008, 09:01 AM

Search Tags


/mathhelpforum @mathhelpforum