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Homework Help: Linear equations, elimination matrix and matlab

  1. Feb 2, 2010 #1
    1. The problem statement, all variables and given/known data
    For part 1 I solve the problem and I got the follow equation and results:

    .25x+.10y+.05z=1.15
    x+y+z=9
    -2y+z=0

    The solution is x=3, y=2, z=4

    Now I have to solve this by hand with the equation in matrix form using elimination matrix

    2. Relevant equations

    EAx = Eb

    3. The attempt at a solution

    A=[.25 .1 .05; 0 -2 1; 1 1 1];
    B= [ 1.15; 0; 9]

    Using Matlab I can solve it like this X= inv(A)*B = x=3, y=2, z=4 but that is not what he wants

    to me the first elimination matrix is E= [1 0 0; 0 1 0; -1 0 1] but is not eliminating anything.
    This may help some but I don't see how:
    http://www.gregthatcher.com/Mathematics/GaussJordan.aspx" [Broken]

    How do I solve this by hand and then input it into matlab?

    Thanks
     
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Feb 2, 2010 #2

    berkeman

    User Avatar

    Staff: Mentor

    Do you mean you need to put the original matrix in row echelon form?

    http://en.wikipedia.org/wiki/Row-echelon_form

    .
     
    Last edited by a moderator: May 4, 2017
  4. Feb 2, 2010 #3
    no! I was given this in part 1:


    which I solve, and is on my first post.

    On the second part I am suppose to do this:

     
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