Discussion about math, puzzles, games and fun.   Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫  π  -¹ ² ³ °

You are not logged in.

## #1 2005-12-14 17:35:37

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?

## #2 2005-12-14 17:57:30

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)

Offline

## #3 2005-12-14 18:06:00

Alfred
Guest

### Re: Help with Sigma Notation

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

## #4 2005-12-14 18:10:07

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)

"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..."

Offline

## #5 2005-12-14 18:14:19

Alfred
Guest

### Re: Help with Sigma Notation

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

## #6 2005-12-14 18:17:15

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)

"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..."

Offline

## #7 2005-12-14 18:52:46

MathsIsFun
Registered: 2005-01-21
Posts: 7,609

### Re: Help with Sigma Notation

Is this it?

$\sum_{k=1}^\infty2^{k+1}-2^{k-1}$

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

Offline

## #8 2005-12-14 19:30:48

ryos
Member
Registered: 2005-08-04
Posts: 394

### Re: Help with Sigma Notation

I think this one is cleaner:

El que pega primero pega dos veces.

Offline

## #9 2005-12-14 22:16:17

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?

"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..."

Offline

## #10 2005-12-14 23:52:44

MathsIsFun
Registered: 2005-01-21
Posts: 7,609

### Re: Help with Sigma Notation

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

Just found this though

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

Offline

## #11 2005-12-15 05:06:03

ryos
Member
Registered: 2005-08-04
Posts: 394

### Re: Help with Sigma Notation

n is the number of iterations.

El que pega primero pega dos veces.

Offline