Question

FAN/MEDAL PLEASE HELP
If anyone is willing to walk me through Sigma Notation, I would greatly appreciate it.

Answer 1

@agent0smith

Answer 2

These are my answer choices, but i would like to know how to do it...
−256
−84
84
86

Answer 3

\[\Large 2(-2)^{n-1}\]plug in n=1
then plug in n=2
...
then plug in n=7

add up all the results

Answer 4

so 2(-2)^1 - 1 = 1
and 2(-2)^2 - 1= -4
and 2(-2)^3 - 1 = 8
and 2(-2)^4 - 1 = -16
and 2(-2)^5 - 1 = 32
and 2(-2)^6 - 1 = -64
and 2(-2)^7 - 1 = 128
so it would equal 85?

Answer 5

First one is not correct.

Answer 6

oh.. oops its 2.... so its actually 86... right?

Answer 7

ok thank you so much, so the n = 1 under the sigma is the starting point and the 7 is the end point?

Answer 8

and you plug in the values within that into the equation next to the sigma, right?

Answer 9

The thing is you should be careful about the exponent. It is to the power of \(n-1\). So, at n=1, the exponent \(n-1=0\), and at n=7, n-1 = 6.

Answer 10

Yep

Answer 11

86 is right

Answer 12

ok! thank you all so so much! now i actually understand the concept! :D yay :)