Question

What is the fifth term of the geometric sequence 5,15,45,...

Answer 1

Answer:

405

Step-by-step explanation:

This is a geometric sequence, so we need the common ratio and the first term

To find the common ratio, we take the second term and divide by the first term

15/5 =3

The common ratio is 3

We are multiplying by 3 each time

The first term is 5

The formula is

an = a1 * (r) ^ (n-1)  where n is the term number

We want the 5th term

a5 = 5 * (3) ^ (5-1)

a5 = 5 *3^4

    = 5 *81

    = 405