Find the least value of n for which

How do I do this?

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- October 17th 2009, 03:33 PMViralFind the least value of n in an arithmetic sequence
Find the least value of n for which

How do I do this? - October 17th 2009, 03:40 PMMatt Westwood
- October 17th 2009, 03:42 PMViral
Hmm, I'm not really sure what you did there =\ . We've never covered that.

- October 17th 2009, 03:44 PMmr fantastic
- October 17th 2009, 03:44 PMMacstersUndead
- October 17th 2009, 03:46 PMViral
Is ?

- October 17th 2009, 03:49 PMMacstersUndead
- October 17th 2009, 03:51 PMViral
Hmm, I kind of understand that. Are there other ways to solve this as our teacher specifically said we should be able to solve all questions with what we have been taught.

- October 17th 2009, 03:52 PMMatt Westwood
- October 17th 2009, 03:56 PMViral
To be honest, I would but I don't know how I'd explain it. We've learned how to calculate all terms in a sequence, how to find a, d, n and l. And this is our first look at the summation notation. If there are other methods, and we've been taught it, it should hit me when I see it.

- October 17th 2009, 03:56 PMmr fantastic
The first term in the sum is 4 - 3 = 1. Therefore a = 1.

The common difference between each term is 4. Therefore d = 4.

There are n terms.

Substitute all that into your formula for the sum of an arithmetic series and then do with the result what I said to do in my first reply. - October 17th 2009, 03:58 PMViral

Just to check, is this the formula for calculating the sum? - October 17th 2009, 04:00 PMmr fantastic
- October 17th 2009, 04:01 PMViral
It's a help forum after all >> . My textbook has been misplaced, hence why I'm here. I'm also here because google brought me here.

- October 17th 2009, 04:07 PMmr fantastic