Question

What is the sum of a 6-term geometric sequence if the first term is 11, the last term is –11,264 and the common ratio is –4?

Answer 1

-9009

Answer 2

I'm still calculating. I'm a little slow, but I like to check my final answer with the pros :)

Answer 3

a1[r^n -1]
Sn= ------- ......Sum of sequence
r-1

last term, b=a1(r^(n-1))

Answer 4

OK. I also got negative 9009 :) I used A.clan formula so it takes me a while