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Homework Help: Really simple matrix reduction

  1. Mar 11, 2009 #1
    1. The problem statement, all variables and given/known data

    I don't know why I keep getting this wrong...some help would be greatly appreciated.

    A =

    [ 0 -6 ]
    [-2 -3 ]

    (1) Write A as a product of 4 elementary matrices:

    Wouldn't that just mean to Reduce Row echelon it, and show it in 4 steps?

    (2) Write A^-1 as a product of 4 elementary matrices

    Wouldn't I just find the inverse of A, and write down the steps?

    I did all that and I got it wrong...so maybe if someone could show me, it would really help me out!

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Mar 11, 2009 #2


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    Homework Helper

    the product of the matrices at the end of each step should give back the original matrix.
  4. Mar 11, 2009 #3
    In this case an elementary matrix means a matrix which you obtain by preforming a single row operation on the identity matrix.

    Yes but you have to express the row operations as a matrix.

    Remember A is expressed as the product of four elementary matrices.

    [tex](A_1 A_2 A_3 A_4)^{-1}[/tex]

    gives what when the brackets are removed.
  5. Mar 11, 2009 #4
    that is what RREF does anyways.

    So if,

    [ -2 -3 ]
    [ 0 -6]

    [1 3/2 ]
    [0 -6 ]

    [ 1 3/2 ]
    [ 0 1 ]

    [1 0 ]
    [0 1 ]

    Is that not the answer in four elementary matrix steps for the first question?

    And for the second question it is the same, but steps on the other side (inverse matrix)?
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