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Homework Help: Linear Algebra, GA=rref(A)

  1. Sep 11, 2008 #1
    So I found the elimination matrices such that [tex]G_3G_2G_1A=rref(A)[/tex] which, but it took way too long. Is there a shorter method?
     
  2. jcsd
  3. Sep 11, 2008 #2

    Defennder

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    I don't understand what were you trying to find. You want to find the matrix E such that EA = reduced row-echelon form of A ?

    If so, I don't see any easy way to get it. Note that the elementary matrix corresponding to a row operation is simply the identity matrix with that same row operation performed on it. Just keep a simple record of all the types of row reduction you did, then you can easily get E from them.
     
  4. Sep 11, 2008 #3

    Defennder

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    Just thought about this a little longer and realised that if all you want is the final matrix G which is a matrix product of all the E's, then one way you could get it would be to juxtapose the identity matrix next to A and and row reduce A to it's reduced row echelon form. The resultant matrix next to rref(A) would be G. If you want the composite E's you'll have to solve as above.
     
  5. Sep 11, 2008 #4
    That's what my classmate told me as well, I haven't verified that method yet.

    I did what you said in the first post, took me forever to get G through all the E's, LOL.
     
  6. Sep 11, 2008 #5
    Lol much quicker!!! :)))
     
  7. Sep 11, 2008 #6

    Defennder

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    Well the quickest way of course would be to use MATLAB. But that's cheating.
     
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