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Homework Help: Stuck on review math problem

  1. Sep 20, 2005 #1
    Hey everyone, I am stuck on this question:
    [tex](2^1)(2^2)(2^3)(2^4)...(2^n) = 210[/tex]

    What is the value of n?

    I'd love to post what I have so far, except that the problem doesn't involve much work, so as soon as I have the first step I'll have the last...and I haven't yet gotten the first (correct) step.

    THANKS!!
     
    Last edited: Sep 20, 2005
  2. jcsd
  3. Sep 20, 2005 #2
    [tex]2^{1+2+3+...+n}[/tex]=210
     
  4. Sep 20, 2005 #3
    don't i feel stupid.... :rofl:

    I was doing the exact same thing only with the tn = a + (n-1)d formula instead of the Sn = n/2[2a + (n-1)d] formula!!!

    Thank you!
     
    Last edited: Sep 20, 2005
  5. Sep 20, 2005 #4
    i found an answer which is not an integer!
     
  6. Sep 20, 2005 #5

    Diane_

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    Homework Helper

    Since 210 is not a multiple of 2, that's to be expected.
     
  7. Sep 20, 2005 #6
    it is contrary to the method, because 1 + 2+ 3 +.. +n indicates that n must be an integer if want to use the arithmetic sequence formulae.
     
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