Nth term of alternating series with two positive terms at beginning

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Discussion Overview

The discussion revolves around determining the nth term of an alternating series that begins with two positive terms, specifically the series 1, 1, -1, 1, -1, 1, -1. Participants explore different approaches to express the series mathematically.

Discussion Character

  • Exploratory, Mathematical reasoning

Main Points Raised

  • One participant suggests that if the first term were removed, the series could be represented as (-1)^(n+1), but questions how to account for the initial term.
  • Another participant proposes writing the series as 1 plus the alternating series, indicating a potential simplification.
  • A third participant questions the validity of defining the first term as a1 = 1 and subsequent terms as an = (-1)n for n > 1, seeking clarity on this approach.
  • A later reply expresses satisfaction with the proposed definition but wonders if there might be a more optimal method.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the best way to express the nth term of the series, with multiple approaches being discussed and no definitive resolution presented.

Contextual Notes

Some assumptions regarding the definitions of terms and the structure of the series remain unaddressed, and the discussion does not resolve the optimal representation of the series.

greg9381
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(I hope this is the right subforum)
I'm talking about the series 1, 1, -1, 1, -1, 1, -1... I thought about it for a long time but I have no idea. If that first term were gone it would just be (-1)^(n+1), but...it's there...
 
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greg9381 said:
(I hope this is the right subforum)
I'm talking about the series 1, 1, -1, 1, -1, 1, -1... I thought about it for a long time but I have no idea. If that first term were gone it would just be (-1)^(n+1), but...it's there...

Just write it as 1 + your alternating series.
 
greg9381 said:
(I hope this is the right subforum)
I'm talking about the series 1, 1, -1, 1, -1, 1, -1... I thought about it for a long time but I have no idea. If that first term were gone it would just be (-1)^(n+1), but...it's there...

What's wrong with a1 = 1, and an = (-1)n for n > 1?
 
Yeah that works, I was just wondering if there was a better way to do it.
 

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