Results 1 to 5 of 5

Math Help - Inverse matrix

  1. #1
    Member
    Joined
    Oct 2009
    Posts
    196
    Thanks
    1

    Inverse matrix

    Find the inverse of the matrix

    A = |-1 0 0 0|
    |0 -1 3 0|
    |0 0 2 0|
    |-3 3 -3 2|

    Thanks!
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Master Of Puppets
    pickslides's Avatar
    Joined
    Sep 2008
    From
    Melbourne
    Posts
    5,236
    Thanks
    28
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Junior Member
    Joined
    Sep 2008
    From
    Edmonton
    Posts
    67
    also
    if you take the matrix A and use a sequence of row operations to reduce it to I
    then those same operations applied to I will give you A inverse

    since you're basically doing (P1)(P2)...(Pn)A = I
    which implies (P1)(P2)...(Pn) = A^-1

    an easy way to do this is to take [A|I] and reduce the left part to I
    what remains on the right will be A inverse

    example:
    1 1
    0 1

    you take
    1 1 1 0
    0 1 0 1

    then your row operations to reduce the left part into I is simply R1-R2
    ==>
    1 0 1 -1
    0 1 0 1
    so the inverse is
    1 -1
    0 1

    now you can do it for the larger matrix
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Member
    Joined
    Oct 2009
    Posts
    196
    Thanks
    1
    "Online Matrix Calculator"

    Thank you for that! Now, I'm on an old computer, so the instructions doesn't show up. But if I did it right, the inverse of the matrix should be:

    -1 0 0 0
    0 -1 3/2 0
    0 0 1/2 0
    -3/2 3/2 -3/2 1/2

    Is this right?
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Member
    Joined
    Apr 2008
    Posts
    191
    Quote Originally Posted by gralla55 View Post
    "Online Matrix Calculator"

    Thank you for that! Now, I'm on an old computer, so the instructions doesn't show up. But if I did it right, the inverse of the matrix should be:

    -1 0 0 0
    0 -1 3/2 0
    0 0 1/2 0
    -3/2 3/2 -3/2 1/2

    Is this right?
    Yes, it's correct. I used Matlab and ended up with the same answer as you.

    Code:
    A =
    
        -1     0     0     0
         0    -1     3     0
         0     0     2     0
        -3     3    -3     2
    
    EDU>> inv(A)
    
    ans =
    
       -1.0000         0         0         0
             0   -1.0000    1.5000         0
             0         0    0.5000         0
       -1.5000    1.5000   -1.5000    0.5000
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. [SOLVED] Finding the inverse of a matrix using it's elementary matrix?
    Posted in the Advanced Algebra Forum
    Replies: 3
    Last Post: March 7th 2011, 07:08 PM
  2. [SOLVED] Derivative of a matrix inverse and matrix determinant
    Posted in the Advanced Algebra Forum
    Replies: 1
    Last Post: February 24th 2011, 09:18 AM
  3. inverse matrix
    Posted in the Algebra Forum
    Replies: 1
    Last Post: December 2nd 2010, 09:13 PM
  4. Replies: 3
    Last Post: March 1st 2010, 07:22 AM
  5. Inverse Matrix help!
    Posted in the Algebra Forum
    Replies: 7
    Last Post: November 24th 2008, 03:50 PM

Search Tags


/mathhelpforum @mathhelpforum