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MOD x explination please

  1. Mar 3, 2009 #1
    I am having some troubles with the beggining ideas about modulus and absolute values etc...

    i understand the basics about it but get a bit confused when they ask for the sum of different expressions or the product of different expressions

    |x - 1| + |x + 1| < 1


    |x - 2|.|3x + 1| >2

    if someone could explain this so its quite easy to understand and NOT just complete these examples but explain the concepts!

    Much appreciated
  2. jcsd
  3. Mar 3, 2009 #2


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    Science Advisor

    The general idea is to break up the question into several questions without | |. For example - the first expression:
    For x > 1, (x-1)+(x+1) > 1, which becomes 2x > 1, or x > 1/2 (all x in range)
    For 1> x > -1, (1-x)+(x+1)>1, which becomes 2 >1. (all x in range)
    For -1 > x, (1-x)-(1+x) > 1, which becomes -2x > 1, or x < -1/2 (all x in range)
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