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Math Help - find a value so that ab=ba

  1. #1
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    find a value so that ab=ba

    hey guys.. kinda confused on how to do this...
    what values of k will make AB=BA
    A = 2 5
    -3 1

    B= 4 -5
    3 k


    what i did was multiply them together, seperately, and then tried to equate the k... didnt work


    thanks!
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  2. #2
    Banned
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    what you did should have worked, you should get 6-3k=-9 and 5k-10=15
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  3. #3
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    the answer is k-5.. how do u get that then?
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  4. #4
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    nevermind i got it... thanks!
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