Math Is Fun Forum

Alfred

Guest

Help with Sigma Notation

I'm new to sigma notation and I'm supposed to put 3 + 6+ 12+ 24 + 48 in it, but I really can't figure out how to do it.  I've tried for so long, but nothing I try works.  Can come help?

MajikWaffle

Member

Registered: 2005-12-14

Posts: 11

Re: Help with Sigma Notation

n <- end of the sequence
Σ (Equation)
k = 1  <- starting

Last edited by MajikWaffle (2005-12-14 17:57:43)

Alfred

Guest

Re: Help with Sigma Notation

I know all that, it's just this problem I can't get.

Ricky

Moderator

Registered: 2005-12-04

Posts: 3,791

Re: Help with Sigma Notation

Don't ask me how I got this, I couldn't tell you.  Just a bunch of guessing and checking:

Summation of k = 1 to n of 2^(k+1) - 2^(k-1)

Last edited by Ricky (2005-12-14 18:11:14)

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"In the real world, this would be a problem.  But in mathematics, we can just define a place where this problem doesn't exist.  So we'll go ahead and do that now..."

Alfred

Guest

Re: Help with Sigma Notation

I couldn't get that to work out.  Are you sure?

Ricky

Moderator

Registered: 2005-12-04

Posts: 3,791

Re: Help with Sigma Notation

2^(k+1) - 2^(k-1)

K = 1:
2^2 - 2^0 = 4 - 1 = 3

K = 2:
2^3 - 2^1 = 8 - 2 = 6

K = 3:
2^4 - 2^2 = 16 - 4 = 12

K = 4:
2^5 - 2^3 = 32 - 8 = 24

And so on.

Last edited by Ricky (2005-12-14 18:17:51)

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"In the real world, this would be a problem.  But in mathematics, we can just define a place where this problem doesn't exist.  So we'll go ahead and do that now..."

MathsIsFun

Administrator

Registered: 2005-01-21

Posts: 7,713

Re: Help with Sigma Notation

Is this it?

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"The physicists defer only to mathematicians, and the mathematicians defer only to God ..."  - Leon M. Lederman

ryos

Member

Registered: 2005-08-04

Posts: 394

Re: Help with Sigma Notation

I think this one is cleaner:

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El que pega primero pega dos veces.

Ricky

Moderator

Registered: 2005-12-04

Posts: 3,791

Re: Help with Sigma Notation

ryos, what's n?

And where can I look up commands for this code?

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"In the real world, this would be a problem.  But in mathematics, we can just define a place where this problem doesn't exist.  So we'll go ahead and do that now..."

MathsIsFun

Administrator

Registered: 2005-01-21

Posts: 7,713

Re: Help with Sigma Notation

It is "LaTeX" and I don't know it very well.

Just found this though

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"The physicists defer only to mathematicians, and the mathematicians defer only to God ..."  - Leon M. Lederman

ryos

Member

Registered: 2005-08-04

Posts: 394

Re: Help with Sigma Notation

n is the number of iterations.

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El que pega primero pega dos veces.