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

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