Question

What is the sum of an 8-term geometric series if the first term is 15 and the last term is -4,199,040?

Answer 1

-3,599,175
-3,359,230
-3,119,285
-2,879,340

Answer 2

NTH TERM OF GP:;
\[a _{n}=ar ^{n-1}\] where a denotes first term
r denotes common ratio
\[a _{n} \] denotes last term of sequence

Answer 3

here
\[a _{8}=-4199040\]
a=15
n=8

Answer 4

find out r from this formula

Answer 5

then you can substitute it in sum formula

Answer 6

okay, um. is r = -6?

Answer 7

yes.........right
good