Question

Find the 8th term and the sum of the first 8 terms of the geometric sequence

Answer 1

a8 = 1/64

S8 = - 85/64

Explanation:

1/-2 = - 1/2

Common ratio: - 1/2

an = a1 * r^(n-1)

a8 = -2 * - 1/2 ^ (8-1)

a8 = -2 * (-1/128)

a8 = 1/64

Sn = a1 * (1 - r^n)/(1-r)

Sn = [1 - (-1/2)^8] / 1 - (-1/2)

s8 = -2 * 85/128

S8 = - 85/64