Question

help is this right!?

Answer 1

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

159,964?????

Answer 2

Seems to be\[-3((-1)^n6^n)\]With the first one n=0.

Answer 3

As 18/3=6 and 108/18=6 I knew there was a 6^n in there, and a (-1)^n as the +ve/-ve alternates

Answer 4

now i got 411,772..
that doesn't seem right either.

Answer 5

-119973. The is by adding: \[-3 \sum_{x=1}^{7} (-6)^{x-1}\]

Answer 6

oh alright thank youuuuuu so much.

Answer 7

You're welcome.