Question

WILL MEDAL. given the first 4 terms and the number of terms of the geometeric series, find the finite sum. 2-10+50-250, n=8

Answer 1

well you have a 1st term of a = 2 what's the common ratio..?

Answer 2

i got the answer of -132,208

Answer 3

now I need a calculator

Answer 4

ummm I think you have a calculation error

Answer 5

2,-10,+50,-250, with 8 terms: 8

basically: \(\Large\color{blueviolet}{ \displaystyle \sum_{ k=1 }^{ 8 } 2(-5)^k}\)

Answer 6

that is how I see the question

Answer 7

if you use the sum of a geometric series formula

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

you know a = 2 and n = 8.... you need to find r.

then substitute all 3 values to find the sum

Answer 8

-130,208?

Answer 9

that looks a lot better