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Homework Help: A proof question

  1. Nov 21, 2008 #1
    for "a" and "b" are real numbers prove that:
    http://img505.imageshack.us/img505/5329/26310844lw6.gif [Broken]

    whats the meaning of MAX[a,b] and MIN[a,b]

    how am i supposed to prove that

    Last edited by a moderator: May 3, 2017
  2. jcsd
  3. Nov 21, 2008 #2


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    Max[a, b] is "maximum of a and b" or simply the larger of the two numbers.

    You are asked to prove that max[a,b] = (1/2)(a+ b+ |a- b|)

    As always with absolute value problems, break it into to cases: a> b and a< b, and show that the two sides are the same in each of those cases.
  4. Nov 21, 2008 #3
    but there are variables
    even if i presume that a>b
    i cant develop into a formula
    i cant put it into the given expression
  5. Nov 21, 2008 #4
    the only thing i can do with the given expression
    is to split |a- b| into two cases
    a-b>0 ->a>b
    which gives me :
    (1/2)(a+ b+ a- b)=a

    a-b<0 a<b:
    (1/2)(a+ b-a+ b)=b

    i got a similar resolt but it didnt came from
    that in the i say "if a>b ..."
  6. Nov 21, 2008 #5


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    That's a proof, isn't it?

    What's wrong with that? :confused:

    (and why didn't you type out the question, and make it easier for every one?)
  7. Nov 21, 2008 #6
    in the first post i typed the question and added a link to the formula

    regarding the question:
    i did it correctly?
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