# A quick question on Summations.

1. May 5, 2009

### psycho2499

I can never remember how to expand a summation in to form: $$\sum$$nk=1(22). Thats just a recent example. I can't remember the expansion form any sort of summation really except when it has a defined upper bound.

2. May 5, 2009

### Dick

The upper bound is n and the lower bound is 1 isn't it? Looks to me like 4*n.

3. May 5, 2009

### psycho2499

sorry i meant to say 2^n for the eq.

4. May 5, 2009

### Dick

Then isn't it n*2^n, or did you mean 2^k? Then it's just a finite geometric sum.

5. May 5, 2009

### psycho2499

this is what i get for only half paying attention to what i type. damn finals. 2^k, Sorry bout that

6. May 5, 2009