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Absolute value

  1. Mar 7, 2008 #1
    I found a study page which lists the absolute value of x for x<0 as -x. I think this has to be a typo. The study area is real analysis. Does anyone have better information? Maybe it is some special notation?
  2. jcsd
  3. Mar 7, 2008 #2


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    I'm pretty sure this is the standard definition.

    |x| = x if x>=0 and -x if x<0
  4. Mar 7, 2008 #3
    Ouch. I thought absolute value was a difference expressed as a positive number.

    I see in wikipedia that an absolute value is always positive. But the notation seems to indicate otherwise. What gives?

    arghh. I see it now. The notation is saying to reverse the sign of a negative number. Thanks
    Last edited: Mar 7, 2008
  5. Mar 7, 2008 #4
    It is. If x < 0 say x = -5 then you would want the |x| = 5 which is -x.
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