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Math Help - am i being stupid?

  1. #1
    Junior Member
    Joined
    Apr 2008
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    62

    am i being stupid?

    I have this:

    -6 + Sqrt 6^2 - 4*1*6
    2*1

    so following this through i ended up at:

    -3 + Sqrt 6

    but the answer in my book is saying i should have the square root of 3.
    How does square root of 12 divided by 2 end up as square root of 3 instead of 6 (12/2)??

    probably really simple but after reading about eigenvalues and dynamic matrix for the last hour my heads just hurts......
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  2. #2
    Super Member
    Joined
    Sep 2007
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    Quote Originally Posted by thermalwarrior View Post
    I have this:

    -6 + Sqrt 6^2 - 4*1*6
    2*1

    so following this through i ended up at:

    -3 + Sqrt 6

    but the answer in my book is saying i should have the square root of 3.
    How does square root of 12 divided by 2 end up as square root of 3 instead of 6 (12/2)??

    probably really simple but after reading about eigenvalues and dynamic matrix for the last hour my heads just hurts......
    \frac{-6 \pm \sqrt{6^2 - (4)(1)(6)}}{(2)(1)}

    \frac{-6 \pm \sqrt{12}}{2}

    \frac{-6 \pm \sqrt{(4)(3)}}{2}

    \frac{-6 \pm \sqrt{(4)}\sqrt{(3)}}{2}

    \frac{-6 \pm 2 \sqrt{(3)}}{2}

    -3 \pm \sqrt{3}
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  3. #3
    Junior Member
    Joined
    Apr 2008
    Posts
    62
    what an incredible ***** !


    thanks for the quick answer
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