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Difference of squares

  1. Jan 19, 2008 #1
    I'm looking for patterns and if you can add to things I noticed before working it out, that would be good :-]

    1. [tex](a+b+c)(a+b-c)=a^2+b^2+c^2+2ab[/tex]

    I noticed that b+c and b-c compensated for each other.

    2. [tex](a+b+c)(a-b-c)=a^2-b^2-c^2-2bc[/tex]

    a+b and a-b compensated for each other and the fact that it's b+c and -b-c, is the reason that it was -2bc?

    3. [tex](a+b-c)(a-b+c)=a^2-b^2-c^2+2bc[/tex]

    a+b and a-b compensated for each other, Now I figured from problem 2 that it would be 2bc again, but I didn't predict the sign correctly?
    Last edited: Jan 19, 2008
  2. jcsd
  3. Jan 19, 2008 #2


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    Not sure I will be helpful here but all I can see is that

    and the same for the 3rd one.

    for the first one:

    EDIT: oh wait...that is not what you were talking about...my bad
  4. Jan 19, 2008 #3
    Nope, lol. But I didn't even think about what you were doing (grouping then putting it in a more visible manner). Thanks, still helped!
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