Question

what is the sum of the geometric sequence: -4, 24, -144... if there are 10 terms?

Answer 1

http://www.mathsisfun.com/algebra/sequences-sums-geometric.html

Answer 2

If a = -4
r = -6
n = 10

\[Sn = a[\frac{ 1-r ^{n} }{ 1-r }]\]

substitute and solve.