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Math problem

  1. Dec 28, 2012 #1
    Math problem!!!

    1. The problem statement, all variables and given/known data

    Is (a+b)^2 ALWAYS equal to a^2+2ab+b^2?

    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Dec 28, 2012 #2

    Dick

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    Re: Math problem!!!

    Yes, if a and b represent objects in a commutative ring like the real numbers. If multiplication is not commutative, (for example a and b are matrices) then (a+b)^2=a^2+ab+ba+b^2 which is not generally the same. Why do you ask?
     
    Last edited: Dec 28, 2012
  4. Dec 28, 2012 #3

    Mentallic

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    Re: Math problem!!!

    If a and b are numbers as they should be if you're in high school, then yes, they're always equal. Why?

    [tex](a+b)^2[/tex]
    [tex]=(a+b)(a+b)[/tex]
    [tex]=a(a+b)+b(a+b)[/tex]

    And I'm sure you can expand out the rest.
     
  5. Dec 28, 2012 #4

    SteamKing

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    Re: Math problem!!!

    Math formulas generally don't have expiration or 'black out' dates.
     
  6. Dec 29, 2012 #5
    Re: Math problem!!!

    Well this was weird.. xD
     
  7. Dec 29, 2012 #6
    Re: Math problem!!!

    Is p+q+r=p+q+s never valid?
     
  8. Dec 29, 2012 #7
    Re: Math problem!!!

    Only if r=s. Why do you want to know?
     
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