Question

What is the sum of a seven-term geometric series if the first term is -2, the last term is

-31,250, and the common ratio is -5?

Answer 1

-26042

Explanation:

sum of a finite geometric series =

`(a_1(1-r^n))/(1-r)`

here, a1 is the first term, r is the common ratio, and n is the number of terms

a1 = -2

r = -5

n = 7

`(a_1(1-r^n))/(1-r) = (-2(1-(-5)^7))/(1-(-5)) = -26042`