Question

What is the explicit formula for this geometric sequence? 64, 16, 4, 1, ...

Answer 1

Option C

Explanation:

=>
`a_(n) = a_(1) * r^{(n-1)`

Where a1 = 64, r = 1/4

So,

=>
`a_(n) = 64 * ((1)/(4)) ^(n-1)`

Answer 2

C.

Explanation:

Explicit Formula: an = a1(r)^(n-1)

Our r = 1/4 because to get 64 down to 16 you need to divide by 4 or multiply by 1/4

Our a1 is the 1st term of the sequence, which is 64.

Plug it in: an = 64(1/4)^(n-1)

So our only viable option is C.