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Why does a = -a?

  1. Oct 16, 2014 #1
    I've been messing around with numbers (as you do) and I'm wondering why this occurs..
    lets let a = b-c.
    = √(b-c)
    For example if you let a = 1, b = 2, and c = 1.
  2. jcsd
  3. Oct 16, 2014 #2


    Staff: Mentor

    The step above is where the problem is. You're using the property that ##\sqrt{ab} = \sqrt{a}\sqrt{b}##
    There are restrictions on this and some of the other square root properties - both a and b have to be nonnegative.
    Last edited: Oct 16, 2014
  4. Oct 16, 2014 #3
    That makes sense. Thanks.
  5. Oct 18, 2014 #4


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    [itex]\sqrt[2]{-1} = \pm i. [/itex] The choice of the '+' or '-' depends on the situation. So your result is '[itex] a = \pm a [/itex]' where you must decide which sign is correct.
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