Question

What is the sum of the geometric sequence –3, 18, –108, … if there are 8 terms?

Answer 1

use
\[\Large S=\frac{a_{1}(1-r^n)}{1-r}\]
where a1=-3
n=8
r=-6

Answer 2

sami-21 is correct .. then, distribute the value to the formula .. and soon, you will get the answer ...