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Linear Algebra Row Reduction?

  1. Sep 12, 2011 #1
    Linear Algebra Row Reduction???

    1. The problem statement, all variables and given/known data

    This question is frustrating me, and I might be missing the obvious, I tend to make algebraic mistakes, but I don't know what I'm doing wrong here!

    I'm trying to solve this system using row reduction:

    x-5y+4z=-3
    2x-7y+3z=-2
    -2x+y+7z=-1

    Note this does not have to be in reduced echelon form, just regular echelon form.





    3. The attempt at a solution


    Okay so I started like this:
    Note: "l" indicated the bar representing "=" sign
    1 -5 4 l -3
    2 -7 3 l -2 --> I then used -2(2nd row)+1st row
    -2 1 7 l -1 --> And 2(1st row)+ 3rd row

    To get:

    1 -5 4 l -3
    0 3 -5 l 4
    0 -9 15 l -7
    I'm trying to remove the -9 in the third row but can't seem to do it without the 15 becoming zero.

    Any help please?
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Sep 12, 2011 #2
    Re: Linear Algebra Row Reduction???

    HINT: Some problems have more then 1 solution, some don't have any. [what is yours case?]
     
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