Question

Find a formula for the nth term of the geometric sequence. Assume the n begins with 1. a1=18, a2=9​

Answer 1

Option E

Explanation:

Explicit formula of a geometric sequence is,

`T_n=a_1(r)^(n-1)`

Here,
`a_1=` First term

`r=` common ratio

`n=` number of terms

If,
`a_1=18` and
`a_2=9`

Common ratio of the sequence
`r=(a_2)/(a_1)`

`r=(9)/(18)`

`r=(1)/(2)`

By substituting these values in the formula,

`T_n=18((1)/(2) )^(n-1)`

Therefore, Option E is the answer.