Finding the general expression of the nth term

  1. Jul 6, 2012 #1
    1. The problem statement, all variables and given/known data
    Given successive terms of numbers starting from the 1st term:
    11, 21, 35, 53, 75, 101,...
    What is the general expression of the nth term? where n is positive integer

    2. Relevant equations

    3. The attempt at a solution
    Can't find a good attempt.
  2. jcsd
  3. Jul 6, 2012 #2


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    Staff Emeritus
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    Could this be an arithmetic or geometric sequence??
  4. Jul 6, 2012 #3


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    Homework Helper

    Form a new sequence from the differences between successive terms.
  5. Jul 6, 2012 #4
    sorry I don't know...

    how will you determine a general expression for it in this problem without trial and error?

    is it like finding a needle in the ocean?
  6. Jul 6, 2012 #5


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    Staff: Mentor

    look at the terms, then form a sequences of differences and what do you get?

    10 , 14, 18, 22, 26 ...

    look at the differences as a sequence and what do you see?

    write an expression to generate the differences sequence

    term(n)= term(0) + 4*(n-1) where n=1, 2, 3, 4...

    then write an expression to generate your sequence using the differences expression

    TERM(n) = TERM(0) + ...
  7. Jul 6, 2012 #6
    Ouw... I think you can use the Sn to calculate the Un...
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