Question

what is the sum of a 7-term geometric series if the first term is -11 and the last term is -171,875 and the common ratio is -5?
PLEASE HELP ME ILL GIVE MEDALS

Answer 1

@yanny123 do you know ?

Answer 2

No actually trying to figure it out

Answer 3

Sum of a GP is given by
\[a(r^n-1)/(r-1)\]
where a is first term
r is ratio
n is no. of terms
so
\[-11((-5)^7-1)/((-5)-1)=-143231\]

Answer 4

You are awsome thanks for the explanation too! i see what i was doing wrong now

Answer 5

@anupsunni

Answer 6

Thanx hav fun

Answer 7

@destenimarie