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!

Absolute Value Problem

  1. Dec 16, 2012 #1
    I'm currently reviewing pre-calculus material and encountered a little problem with an absolute value expression.


    Now the way I learned absolute value expressions was that there's a positive and a negative case. So I got:

    3-x=x-3 x=3 and -(3-x)=x-3 gives 0=0. Stupid question, but isn't 0=0 in general valid for all values of x? And I don't understand how you get to the solution x≥3.
  2. jcsd
  3. Dec 16, 2012 #2


    User Avatar
    2017 Award

    Staff: Mentor

    If you distinguish two different cases, you should keep in mind where those cases apply. Here, your case ##3-x \leq 0## is valid for ##x \geq 3## only.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook