diketahui deret geometri Sk = 54+18+6+2+....+Uk. tentukan nilai S7 !

[tex]a = 54[/tex]
[tex]r = \frac{U_{2}}{U_{1}}[/tex]
[tex]r = \frac{18}{54} [/tex]
[tex]r = \frac{1}{3} [/tex]

[tex]S_{n}= \frac{a(1-r^{n})}{1-r} [/tex]
[tex]S_{7}= \frac{54(1- \frac{1}{3}^{7})}{1-\frac{1}{3}} [/tex]