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Math Help - am I wrong here!?

  1. #1
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    Question am I wrong here!?

    In the book I am working from I was asked to solve the following:

    \sqrt{(3+4i)(4i-3)}

    This is how I worked it out:

    = \sqrt{12i-9+16i^2-12i}

    = \sqrt{-9+16i^2}

    = \sqrt{-9-16}

    = \sqrt{-25}

    = 5i


    Question, did I worked this problem wrong?! as I finished working it out I checked with the book's answer and I was given this as an answer {-1, 1}.

    Could that book have a missprint or is it me?


    Much thanks in advance!!!
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  2. #2
    GAMMA Mathematics
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    How could [-1,1] be an answer to this problem? We are looking for a number, not an interval. You may have looked at the wrong key. If not, the answer in the key is wrong.
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  3. #3
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    Quote Originally Posted by colby2152 View Post
    How could [-1,1] be an answer to this problem? We are looking for a number, not an interval. You may have looked at the wrong key. If not, the answer in the key is wrong.
    ..then it must have been a misprint on the part of the publishers!!

    ......OK, thank you very much, now I know this is going to be one hard semster
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