Question

Write the explicit formula for the geometric sequence.

64, 32, 16, 8, ...

A) an = 8 · 4n-1

B) an = 8 · 2n-1

C) an = 32 · 0.5n-1

D) an = 64 · 0.5n-1


Which answer?

Answer 1

D

Explanation:

the n th term ( explicit formula ) of a geometric sequence is

•
`a_(n)` =
`a_(1)`
`(r)^(n-1)`

where r is the common ratio and
`a_(1)` the first term

here r =
`(8)/(16)` =
`(16)/(32)` =
`(1)/(2)` and
`a_(1)` = 64, hence

`a_(n)` = 64
`(0.5)^(n-1)` → D