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# Summation

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1. What is the standard result for this?
2. (Original post by will'o'wisp)

What is the standard result for this?
It's a geometric progression, whose sum you can look up.
3. (Original post by atsruser)
It's a geometric progression, whose sum you can look up.
Really? where d=can you find this? i couldn't find anything specific
4. sum up 3^r beginning with r=1 for n terms
5. (Original post by TSRPAV)
sum up 3^r beginning with r=1 for n terms
thanks
6. (Original post by will'o'wisp)
Really? where d=can you find this? i couldn't find anything specific
Have you come across the idea of a GP and its sum before? If so, this is a standard result. To do it longhand, start with:

then form , subtract this from and rearrange to get

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Updated: October 1, 2016
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