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Math Help - Square roots

  1. #1
    Senior Member sfspitfire23's Avatar
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    Square roots

    Solve \frac{3}{\sqrt{2}} \times (2\sqrt{3}-6\sqrt{3})

    First, I rationalize the first fraction and get \frac{3\sqrt{2}}{2} and then multiply to get \frac{-9\sqrt{6}}{2}

    Is this correct?
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  2. #2
    Senior Member eumyang's Avatar
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    \begin{aligned}<br />
\dfrac{3}{\sqrt{2}} \times (2\sqrt{3}-6\sqrt{3}) &= \dfrac{3}{\sqrt{2}} \cdot \dfrac{\sqrt{2}}{\sqrt{2}}(-4\sqrt{3}) \\<br />
&= \dfrac{3\sqrt{2}}{2} \cdot (-4\sqrt{3}) \\<br />
&= \dfrac{12\sqrt{6}}{2} \\<br />
&= -6\sqrt{6}<br />
\end{aligned}

    EDIT: Miscopied the problem...
    Last edited by eumyang; August 3rd 2010 at 08:24 AM.
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  3. #3
    Senior Member yeKciM's Avatar
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    Quote Originally Posted by sfspitfire23 View Post
    Solve \frac{3}{\sqrt{2}} \times (2\sqrt{3}-6\sqrt{3})

    First, I rationalize the first fraction and get \frac{3\sqrt{2}}{2} and then multiply to get \frac{-9\sqrt{6}}{2}

    Is this correct?

    u have done this :

     \sqrt{2} \sqrt{3} = \sqrt{6}

    i hope u didn't


    result should be :

    -6\sqrt{2}\sqrt{3}
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  4. #4
    Senior Member sfspitfire23's Avatar
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    eumyang i think you did the wrong problem
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  5. #5
    Senior Member eumyang's Avatar
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    Yeah, fixed it now.
    Quote Originally Posted by yeKciM View Post
    u have done this :

     \sqrt{2} \sqrt{3} = \sqrt{6}

    i hope u didn't
    Why not? It's perfectly valid.

    result should be :

    -6\sqrt{2}\sqrt{3}
    When I learned this, it's okay to leave it like this: -6\sqrt{6} because there are no perfect square factors of 6.
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  6. #6
    Senior Member yeKciM's Avatar
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    Quote Originally Posted by eumyang View Post
    Yeah, fixed it now.

    Why not? It's perfectly valid.


    When I learned this, it's okay to leave it like this: -6\sqrt{6} because there are no perfect square factors of 6.

    aaaaah sorry I was looking in something else ... sorry (for some reason i was going to addition)
    lol here like 38+C and I'm starting to act very very stupid
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