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Find a formula that generates a sequence

  1. Nov 19, 2012 #1
    1. The problem statement, all variables and given/known data

    Find a formula that generates the sequence:

    2/(3 x 4), -3/(4 x 5), 4/(5 x 6), -5/(6 x 7), . . .

    2. Relevant equations

    3. The attempt at a solution

    Here is what I have so far:

    a_n = -1(n/((n + 1)(n + 2)))

    Now, I'm stuck. The formula generates a negative number every time. I need a negative number every other time.
    Any suggestions?
    Last edited: Nov 19, 2012
  2. jcsd
  3. Nov 19, 2012 #2


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    Science Advisor
    Homework Helper

    Use something like (-1)^n?
  4. Nov 19, 2012 #3
    Yeah, that will work. Thanks!
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