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What's the mistake here?

  1. Apr 29, 2012 #1
    What's the mistake here? hehe

    http://a7.sphotos.ak.fbcdn.net/hphotos-ak-snc6/64102_341098562596296_100000884664248_973353_615500462_n.jpg [Broken]
     
    Last edited by a moderator: May 5, 2017
  2. jcsd
  3. Apr 29, 2012 #2

    AlephZero

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    ##2(a^2-ab) = 1(a^2 - ab)##
    Therefore either ##2 = 1## or ##a^2 - ab = 0##
    And ##a^2 -ab## is equal to 0, of course.
     
  4. Apr 29, 2012 #3

    Mentallic

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    Say you wanted to solve the quadratic [itex]x^2=x[/itex]. You wouldn't begin by dividing through by x because that assumes [itex]x\neq 0[/itex]. If x=0 then you've just lost that solution.

    In short, dividing by zero is bad.
     
  5. Apr 29, 2012 #4
    Hmm I see... it was stupid from me not realising that.. lol :D

    Thanks!
     
  6. Apr 29, 2012 #5

    I like Serena

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    Don't try this at home...

    spikedmath-089-dont-try-this-at-home.png
     
  7. May 2, 2012 #6
    In the first line, you say a=b
    and therefore a^2=ab. a^2-ab=0.
    You are dividing by zero even though it's not defined in mathematics. That's the mistake... :D
     
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