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Math Help - Find A

  1. #1
    Senior Member
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    Find A

    if AB =
    [1 1]
    [3 4] and b^{-1} =

    [1 -1]
    [1 2], find A


    I know it's a simple question, i am just not sure if

    AB * B^{-1} = A
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  2. #2
    Banned
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    Quote Originally Posted by wopashui View Post
    if AB =
    [1 1]
    [3 4] and b^{-1} =

    [1 -1]
    [1 2], find A


    I know it's a simple question, i am just not sure if

    AB * B^{-1} = A

    Yes.

    Tonio
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  3. #3
    MHF Contributor

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    By the "associative law", (AB)B^{-1}= A(BB^{-1}). By the definition of "multiplicative inverse", BB^{-1}= I and by the definition of "multiplicative identity", AI= A.
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