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Math Help - complex number algebra

  1. #1
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    complex number algebra

     -2 + \frac{\sqrt{-100}}{2}


    the correct answer is  -1 + 5i

    here's my work out;

     -1 + {\sqrt{-50} =
     -1 + \sqrt{50} \times \sqrt{-1} =

     -1 + \sqrt{25} \times \sqrt{2} i

     -1 + 5\sqrt{2}i

    Can someone please show me where I have gone wrong? Thank you.
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  2. #2
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    Re: complex number algebra

    Quote Originally Posted by Tweety View Post
     -2 + \frac{\sqrt{-100}}{2}


    the correct answer is  -1 + 5i

    here's my work out;

     -1 + {\sqrt{-50} =
     -1 + \sqrt{50} \times \sqrt{-1} =

     -1 + \sqrt{25} \times \sqrt{2} i

     -1 + 5\sqrt{2}i

    Can someone please show me where I have gone wrong? Thank you.
    \frac{\sqrt{-100}}{2} \ne \sqrt{-50}


    \frac{\sqrt{-100}}{2}  = \frac{\sqrt{100} \cdot \sqrt{-1}}{2} = \frac{10i}{2} = 5i
    Thanks from Tweety
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