To find the explicit form we have find r so we divide the second term by the first one so:
[tex]r=-\frac{9}{3}=-3[/tex]Now we know that the formula is:
[tex]\begin{gathered} a_n=a_0r^{n-1} \\ a_n=3(-3)^{n-1} \end{gathered}[/tex]So the answer is option D
