Question

How do you find `a_9` for the geometric sequence `60, 30, 15, ...`?

Answer 1

See explanation.

Explanation:

First we have to find the sequence's first term (`a_1`) and common quotient (`q`).

First term is `a_1=60`

Quotient is `q=a_2/a_1=30/60=1/2`

Now to find the nineth term we can use:

`a_9=a_1xxq^8=60xx(1/2)^8=60/128=15/32`