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Math Help - Multiplying Matrices

  1. #1
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    Multiplying Matrices

    I'm asked to multiply trace matrices, and then subtract them. I'm not sure the order I need to do the questions in. Can somebody help me here?

    tr(BA)-tr(B)tr(A)

    Where A=
    3 -2 7
    6 5 4
    0 4 9

    and B=

    6 -2 4
    0 1 3
    7 7 5
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  2. #2
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    Quote Originally Posted by Hellreaver View Post
    I'm asked to multiply trace matrices, and then subtract them. I'm not sure the order I need to do the questions in. Can somebody help me here?

    tr(BA)-tr(B)tr(A)

    Where A=
    3 -2 7
    6 5 4
    0 4 9

    and B=

    6 -2 4
    0 1 3
    7 7 5
    Multiply BA using the definition. Once you do that to find tr(BA) just add up the ends in the diagnol. Likewise tr(B),tr(A) is the sum in the diagnols.
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  3. #3
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    I got -66 as the answer.. Is this correct?

    tr(BA)= 138
    tr(A)tr(B)= 204
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