# Sigma Notation Problem

1. Feb 17, 2006

### reliquator

Okay, I think this problem relates with sigma notation (I'm not good at it)

the sequence given is 2, 4, 8, 16, 32 ......

It wants you to find the sum from 1-50

So the equation thing is 2^N?

How do you find all the sums again...? Thanks

2. Feb 17, 2006

### Tide

Write out the sum:

$$S = 2 + 2^2 + \cdot \cdot \cdot + 2^{50}$$

If you multiply the sum by 2 you get

$$2S = 2^2 + 2^3 + \cdot \cdot \cdot + 2^{50} + 2^{51}$$

What happens when you subtract the first equation from the second? Can you determine from that what the sum is?

3. Feb 17, 2006

### dextercioby

If you mean something like

$$S=\sum_{k=1}^{50} 2^{k} =...?$$

, i guess the notation shouldn't be too difficult to grasp.
I hope.

Daniel.