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#1 2013-03-08 12:55:17

Registered: 2008-07-01
Posts: 153

Sequence question

Given the sequence

find k
I found the answer as 291, through a tedious guess and check method, but I'd like someone to explain in simpler terms how to find k.

Last edited by infinitebrain (2013-03-08 12:55:30)

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#2 2013-03-08 13:16:56

From: Bumpkinland
Registered: 2009-04-12
Posts: 107,211

Re: Sequence question


You can use differences to get the answer

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.


#3 2013-03-08 15:23:30

Registered: 2011-09-03
Posts: 33

Re: Sequence question


If you subtract consecutive terms, you see that you get:

Subtracting again, you get

You could find the quadratic.  However, another way is to realize that

, which, after solving, gives

Last edited by Stormtangent (2013-03-08 15:25:26)

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