Question

What is the sum of a 7-term geometric series if the first term is 6, the last term is 24,576, and the common ratio is 4?

−32,766
−19,662
19,662
32,766

Answer 1

@jim_thompson5910

Answer 2

i got -32, 766

Answer 3

\[\Large S_n = a*\frac{1-r^n}{1-r}\]

Plug in

a = 6 (first term)
r = 4 (common ratio)
n = 7 (number of terms)

Answer 4

6* 1-4^7/1-4?

Answer 5

I think you meant this right?

\[\Large 6*\frac{1-4^7}{1-4}\]

Answer 6

yeah!

Answer 7

good

Answer 8

compute that with a calculator

Answer 9

make sure you use parenthesis

Answer 10

i got 32766

Answer 11

same here

Answer 12

thanks again

Answer 13

np

Answer 14

will you check this one? @jim_thompson5910

Answer 15

What is the sum of the geometric sequence 1, −6, 36, … if there are 7 terms?

−39,991
−6,665
6,665
39,991 x this one?

Answer 16

Yep

\[\Large S_n = a*\frac{1-r^n}{1-r}\]
\[\Large S_7 = 1*\frac{1-(-6)^7}{1-(-6)}\]
\[\Large S_7 = 39,991\]