Penjelasan dengan langkah langkah:
a = 9
r = 3/9 = 1/3
----------------------------
[tex]\text{S}_{n} = \frac{a(1 - {r}^{n}) }{1 - r} [/tex]
[tex]\text{S}_{8} = \frac{9(1 - { \frac{1}{3} }^{8} )}{1 - \frac{1}{3} } [/tex]
[tex]\text{S}_{8} = \frac{9(1 - \frac{1}{6.561} }{ \frac{3}{3} - \frac{1}{3} } [/tex]
[tex]\text{S}_{8} = \frac{9( \frac{6.561}{6.561} - \frac{1}{6.561} )}{ \frac{3}{3} - \frac{1}{3} } [/tex]
[tex]\text{S}_{8} = \frac{9( \frac{6.560}{6.561} )}{ \frac{2}{3} } [/tex]
[tex] \text{S}_{8} = \frac{ \frac{6.560}{729} }{ \frac{2}{3} } [/tex]
[tex]\text{S}_{8} = \frac{ \cancel{6.560}^{3.280} }{ \cancel {729}^{ \: 243} } \times \frac{ \cancel {3}^{1} }{ \cancel{2}^{1} } [/tex]
[tex]\text{S}_{8} = \bold{ \frac{3.280}{243}} [/tex]