Question

What is the sum of a 11-term geometric series if the first term is 4 and the last term is 4,096?

Answer 1

find r 1st

\[T _{11} = 4r^{10}\]

or

\[4096 = 4r^{10}\]

divide both sides by 4

\[1024 = r^{10}\]

r = 2

use

\[s _{n} = \frac{a(r^n -1)}{r -1}\]

where a = 4, r =2 and n = 11

Answer 2

so wld it be 11264?