Results 1 to 4 of 4

Math Help - Matrices anyone

  1. #1
    Newbie
    Joined
    Oct 2012
    From
    sydney
    Posts
    10

    Matrices anyone


    Hi guys
    I came across this Inverse of matrices by reduction question and need you help.
    Find the inverse of the matrix A= [row1(1 2) row2(5 3)] and use it to solve { x+2y=7, 5x+3y=28 ??????




    Follow Math Help Forum on Facebook and Google+

  2. #2
    Newbie Assassin0071's Avatar
    Joined
    Sep 2012
    From
    Earth
    Posts
    18
    Thanks
    1

    Re: Matrices anyone

    What you have to do is augment A to the identity matrix ( [A | I ] ) and then use elementary row operations until you turn A in to I. By doing these row operation on I in the same order you preformed them on A you will end up with the inverse of A (that is [A | I] turns in to [I | A^-1] after using elementary row operations.) Then you can use the inverse to solve the system (turn the system in to its matrix form then multiply both sides by the inverse). I hope that made sense (and helps).
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Oct 2012
    From
    sydney
    Posts
    10

    Re: Matrices anyone

    But I'm struggling to apply the proper elementary row operations Assassim0071 do you know the sequence of operations i could possibly use??
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Newbie Assassin0071's Avatar
    Joined
    Sep 2012
    From
    Earth
    Posts
    18
    Thanks
    1

    Re: Matrices anyone

    Okay so you have a 2X2 matrix. to reduce that in to the identity you want to get 1's on the diagonals and zero's everywhere else. We can use row operation III (add a multiple of one row to another) to get turn the first entry of the second row to zero by adding -5 times the first row to the second. This elminates the 5 from the second row and turns the 3 in to a -7. Then you can use row operation II (multiply a row by a scalar) to turn the -7 in to a 1. Now we have 1's on the diagonal and only one other non zero entry, all we need to do is get rid of the 2 in the first row. We do this by using row operation III again and add -2 times the second row to the first. This should give you the identiy. So by preforming those exact operations on the identity you should obtain A inverse.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 2
    Last Post: November 25th 2010, 06:34 PM
  2. Total matrices and Commutative matrices in GL(r,Zn)
    Posted in the Advanced Algebra Forum
    Replies: 8
    Last Post: August 16th 2010, 02:11 AM
  3. matrices
    Posted in the Discrete Math Forum
    Replies: 0
    Last Post: February 2nd 2010, 10:36 AM
  4. Matrices represented by Symmetric/Skew Symmetric Matrices
    Posted in the Advanced Algebra Forum
    Replies: 7
    Last Post: October 25th 2008, 05:06 PM
  5. Matrices Again
    Posted in the Advanced Algebra Forum
    Replies: 4
    Last Post: October 2nd 2007, 06:39 PM

Search Tags


/mathhelpforum @mathhelpforum