Question

What is the sum of the geometric sequence -3,18,-108,...if there are 7 terms?

Answer 1

@inkyvoyd may u help me please ?

Answer 2

yawn. use formula

Answer 3

what formula?

Answer 4

\(\Huge a\frac{1-r^n}{1-r}\)

Answer 5

so a is 3 correct? 1-(-6)^3?

Answer 6

you didn't give me answer choices.
and you have to identify a, r, and n to use the formula correctly

Answer 7

-719,835
-119,973
119,973
-719,835

Answer 8

I think the answer will be positive

Answer 9

dude, just use the formula

Answer 10

idk what n is..
so how can i ?

Answer 11

I'm not doing it right because I keep getting answers that are much lower than this.

Answer 12

read please
http://en.wikipedia.org/wiki/Geometric_series#Formula

Answer 13

ugh i still cant figure it out, nvm