Question

What is the sum of a 7–term geometric series if the first term is –11, the last term is –171,875, and the common ratio is –5?

Answer 1

nope

Answer 2

\[S_7=\frac{a(r^7-1)}{r-1}\]

Answer 3

\[\frac{-11((-5)^7-1)}{-5-1}=-143231\]