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Homework Help: Finding Inverse (confused) help Asap

  1. Feb 15, 2007 #1
    #1)2 4
    6 -4

    #2) 1 4
    -2 -8

    #3) 3 1
    0 2

    #4) 1 5 6
    2 1 1
    0 -4 -8
     
  2. jcsd
  3. Feb 15, 2007 #2

    Hurkyl

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    What's confusing?
     
  4. Feb 15, 2007 #3
    how to do the actual inverses....when it comes to the Gauss-Jordan method...i get lost
     
  5. Feb 15, 2007 #4
    these problems are due by 2 tomm
     
  6. Feb 15, 2007 #5

    Hurkyl

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    Well, where do you get lost?
     
  7. Feb 15, 2007 #6
    once you set up the equation (for example #1) to 2x+4z=1
    6x+-4=0

    and go on to set up 2 4| 1 0
    6 -4| 0 1

    ...I don't know what to do from here...this step is where the Gauss-Jordan method comes in...and I don't know how to set up the Row equation....
     
  8. Feb 16, 2007 #7

    Hurkyl

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    Why are you talking about equations? When doing Gaussian elimination, you do nothing but row operations a matrices.
     
  9. Feb 16, 2007 #8
    thats what i am refering to...
     
  10. Feb 16, 2007 #9
    When doing GJ the method is to make the first row, first column a 1, and then 0's in the rest of the rows in that column. Since there is a 2 in R1 C1, you would take 1/2 R1 to make the two a one. Then you have to make the 6 a 0, so you would go: R2 - 6R1 (to get rid of the 6)

    Now your matrix is:

    1 2 | 1/2 0
    0 -10 | -3 1

    or something like that. Now make the -10 a 1 and make the two a 0 after that. Then the right hand side will be your inverse. There is an easier way of finding inverses for a 2x2 matrix using inverses though.
     
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