Absolute value

1. Mar 7, 2008

starkind

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. Mar 7, 2008

quasar987

I'm pretty sure this is the standard definition.

|x| = x if x>=0 and -x if x<0

3. Mar 7, 2008

starkind

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
4. Mar 7, 2008

Diffy

It is. If x < 0 say x = -5 then you would want the |x| = 5 which is -x.