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Homework Help: Guassian Elimination (Row reduction) of 3 simultaneous eqn.

  1. Mar 15, 2009 #1
    1. The problem statement, all variables and given/known data
    I have been given the 3 following simultaneous equations


    and the question is:
    "(a) Solve the equations using Gaussian elimination, showing all your working."

    fairly simple topic i know, but i cant get the answer :/

    3. The attempt at a solution
    Had a few attempts at it.. heres one of them:

    Heres my augmented matrix:


    I switched Row 1 (R1) with Row 2 (R2)


    any from there i can work out x1, x2, x3 etc... but i keep getting reidiculous numbers. And when i check them in the 1st set of equations given, they obviously come out to be wrong.

    I.e for this attempt i get

    x3 = 517/210
    x2 = -2297/1230
    x1 = -19.408

    What am I doing wrong? Any help is much appreciated
  2. jcsd
  3. Mar 15, 2009 #2


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    Gold Member

    On your second step where you did R3-2*R1, 26-(2*-21) does not equal 10
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