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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: 92,930

Re: Sequence question


You can use differences to get the answer

In mathematics, you don't understand things. You just get used to them.

I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.


#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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