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Math Help - Easy Surd, frustrated...

  1. #1
    Junior Member
    Joined
    Oct 2009
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    31

    Easy Surd, frustrated...

    Give in form a+b√2

    (3-√8)

    9-3√8-3√8+4

    13-6
    √8

    13-12
    √2

    book says i'm wrong can't understand why

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  2. #2
    -1
    e^(i*pi)'s Avatar
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    West Midlands, England
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    3,053
    Thanks
    1
    Quote Originally Posted by alibond07 View Post
    Give in form a+b√2

    (3-√8)

    9-3√8-3√8+4 e^(i*pi): Where did +4 come from? (-\sqrt8)^2 = 8

    13-6
    √8

    13-12
    √2

    book says i'm wrong can't understand why

    (3-\sqrt8)^2 = 9-6\sqrt8+8 = 17-6\sqrt8 = 17-12\sqrt2
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  3. #3
    Junior Member
    Joined
    Oct 2009
    Posts
    31
    Thanks got it now, just made a careless mistake with the -√8x-√8.
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