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Quick help

  1. Oct 25, 2007 #1
    I cant seem to figure out how to simplify this!!!!

    n(n+1)/2 + n+1

    which they were able to get (n+1)(n+2)/2 by simplifying that

    and this

    n(n+1)(2n+6)/6 + (n+1)^2

    and they were able to get (n+1)(n+1+1)(2(n+1)+1)/6 out of this one.

    Any help is greatly appreciated.
     
  2. jcsd
  3. Oct 25, 2007 #2
    Try this: surely you know how to "expand" parenthesis, like this: a(b+c) ---> ab + ac.

    So do this both from the given problem expression, and also from the answer. Like this:
    Problem -----> xxx
    Answer ------> xxx
    And try to get the same "xxx" starting from both ends.

    When you have that, you can walk *forward* the steps from the problem, and then *backward* the steps from the solution:
    Problem ------> xxx -------> Answer.
     
  4. Oct 25, 2007 #3
    ok i did that but for the first one i get

    (n^2 + n)/2 + n + 1

    =

    n^2 + n + n + 1/2

    = n^4 + 1/2

    but this does not equal (n+1)(n+2)/2
     
  5. Oct 25, 2007 #4
    You have only expanded the parenthesis on the initial problem... but have not expanded them yet on the solution. Try expanding (n+1)(n+2)/2.

    And hey! Watch out, the /2 is dividing (n^2 + n), and only those two. Try again the first part.
     
    Last edited: Oct 25, 2007
  6. Oct 25, 2007 #5
    ooo I see I got it.. Thanks for the help!!
     
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