Question

Sum of geometric sequences!

Answer 1

Question #11

Answer 2

\[\frac{a_1(1-r^n)}{1-r}\] or
\[\frac{a_1(r^n-1)}{r-1}\]`

Answer 3

use a calculator for sure
\[\frac{128(1-(\frac{1}{2})^{18})}{1-\frac{1}{2}}\]

Answer 4

it is going to be real real close to \(2\times 128=256\)

Answer 5

http://www.wolframalpha.com/input/?i=256%281-%281%2F2%29^%2818%29%29