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Homework Help: Simplifying Surds

  1. Sep 8, 2005 #1
    Ok here is my problem, I am not sure how to simplify surds with additions and subtractions in them such as ones like this:

    http://img212.imageshack.us/img212/474/math010iz.gif [Broken]

    At the moment I have managed to simplify it to this:

    http://img212.imageshack.us/img212/2011/math026eg.gif [Broken]

    However it is not simplified as possible, can someone give me some words of wisdom? Any help greatly appreciated!
    Last edited by a moderator: May 2, 2017
  2. jcsd
  3. Sep 8, 2005 #2


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    In this case, 80 = 4 x 20, so [itex]\sqrt{80}=\sqrt 4 \times\sqrt {20}=2\sqrt {20}[/itex].

    Therefore [itex]\sqrt{20}+\sqrt{80}= (1+2)\sqrt{20}=3\sqrt{20}[/itex], which is [itex]3\times 2\times\sqrt 5 = 6\sqrt 5[/itex].
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