Question

Find S8 for the series -2 + -10 + -50 + -250

Answer 1

Here is a good example that would help you a lot!

http://www.algebra.com/algebra/homework/Sequences-and-series/Sequences-and-series.faq.question.398922.html

Answer 2

wowww @Miracrown u sooo smart, it works
Sn = (a*(1-r^n)) / (1-r)
a = -2
r = 5
n = 8

S8 = -1953??