Answer:
D
Step-by-step explanation:
the n th term ( explicit formula ) of a geometric sequence is
• [tex]a_{n}[/tex] = [tex]a_{1}[/tex][tex](r)^{n-1}[/tex]
where r is the common ratio and [tex]a_{1}[/tex] the first term
here r = [tex]\frac{8}{16}[/tex] = [tex]\frac{16}{32}[/tex] = [tex]\frac{1}{2}[/tex] and [tex]a_{1}[/tex] = 64, hence
[tex]a_{n}[/tex] = 64[tex](0.5)^{n-1}[/tex] → D
