Rumus suku ke -n pada barisan geometri 9,27,81,243...adalah

[tex]$\begin{align}U_n&=ar^{n-1}\\&=9\times3^{n-1}\\&=3^2\times3^{n-1}\\&=3^{2+n-1}\\&=\boxed{3^{n+1}}\end[/tex]

r = 3
a = 9
[tex]un = a {r}^{n - 1} \\ un = 9. {3}^{n - 1} = {3}^{2} x {3}^{n - 1} \\ = {3}^{2 + n - 1} = {3}^{1 + n} [/tex]