Question

How do you write a rule for the nth term of the geometric sequence and then find `a_5` given `a_1=17, r=-2`?

Answer 1

`a_5=272.`

Explanation:

In the Usual Notation for Geo. Seq.,

`a_n=a_1*r^(n-1), n in NN.`

With, `a_1=17, and, r=-2,` we have,

`a_n=17(-2)^(n-1), n in NN.`

Accordingly, `a_5=17(-2)^(5-1)=(17)(16)=272.`