Question

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

Answer 1

Answer:

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