Stuck on review math problem

  • Thread starter rocketboy
  • Start date
  • #1
rocketboy
243
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:

Answers and Replies

  • #2
Leong
382
2
[tex]2^{1+2+3+...+n}[/tex]=210
 
  • #3
rocketboy
243
1
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:
  • #4
Leong
382
2
i found an answer which is not an integer!
 
  • #5
Diane_
Homework Helper
393
1
Leong said:
i found an answer which is not an integer!

Since 210 is not a multiple of 2, that's to be expected.
 
  • #6
Leong
382
2
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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