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How do I sum this series?

  • Thread starter pyrosilver
  • Start date
  • #1
39
0

Homework Statement



1/2 + 2/4 + 3/8 + 4/16 + 5/32 + ...

Homework Equations





The Attempt at a Solution



The only headway I've made is that this is ∑ n/(2^n). how do I go about summing this?
 

Answers and Replies

  • #2
lanedance
Homework Helper
3,304
2
how about starting by adding up the first few terms and looking for a pattern with n terms
 
  • #3
Dick
Science Advisor
Homework Helper
26,258
618
Define f(x)=x^n/2^n. If you find that then your sum just might be related to f'(x) at x=1.
 

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