Question

Find the 15th term of the geometric sequence 9,18,36

Answer 1

147,456

Geometric sequence: 9, 18, 36

Common ratio = r = 18/9 = 2

First term : a_1 = 9

Nth term : a_n = a_1 * r^(n - 1)

a_n = 9 * (2)^(n -1)

We want a_15, the 15th term

a_15 = 9*2^(15 -1)

a_15 = 9*2^14 = 9*16,384 = 147,456‬