1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

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


    User Avatar
    Science Advisor
    Gold Member
    2017 Award

    [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.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook