Question

here is a geometric series in summation notation

what is the sum of the series?

Answer 1

a. -122
b. 44
c. -44
d. 172
e. -84

Answer 2

here first tem is 4
and then common ratio is -2

use S=a.(r^n -1)/(r-1)

thus here reqd sum is 4(-128-1)/(-2-1) =4*43 =172