Question

What is the sum of the geometric sequence –4, 24, –144, … if there are 6 terms?


–159,963

26,660

26,661

159,963

Answer 1

sum of a geometric series is given by:\[\sum_{k=0}^nar^k=\frac{a(1-r^{n+1})}{1-r}\]in your case:
a=-4
r=-6
n=6