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Solving a system with the inverse of a matrix.

  1. Jan 18, 2013 #1
    1. The problem statement, all variables and given/known data
    a)Use Gauss-Jordan elimination to find the inverse of A =
    [ 2 1 4 ]
    [ 1 1 2 ]
    [ -2 -3 -2 ]

    b) Use the result from part a) to find the solution of the following system.

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

    2. Relevant equations



    3. The attempt at a solution

    My problem is not with part a), I quite easily found the inverse of the matrix. What I am not understanding is what exactly they are asking me to do for part b). How can I use the inverse of one matrix to solve for another? Any help is greatly appreciated.
     
  2. jcsd
  3. Jan 18, 2013 #2

    rock.freak667

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    If you change

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

    into a matrix equation in the form of Bx=C, what would B, X and C be?
     
  4. Jan 18, 2013 #3

    Dick

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    I'm with thatguythere. I can't see that the matrix in part b) is related in any simple way to the matrix in part a). I'm suspecting the somebody goofed when assembling the problem.
     
  5. Jan 18, 2013 #4
    I contacted my TA and it is indeed a mistake. It should be
    2x + y + 4z = 5
    x + y + 2z = -1
    -2x -3y -2z = 2
    I should be able to manage now, thanks.
     
  6. Jan 18, 2013 #5

    rock.freak667

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    Ah well, I didn't calculate the inverse, so I assumed it one of those problems where the matrix equation would be A-1x=B
     
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