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Given the geometric sequence:   9,  3,  1,  ...  .      Find S6

 Apr 14, 2015

Best Answer 

 #1
avatar+21978 
+5

Given the geometric sequence:   9,  3,  1,  ...  .      Find S6

ratio r =  $$\small{\text{$
\frac{3}{9}=\frac{1}{3} $}}$$
 and $$\small{\text{$a=9$}}$$ so

$$\small{\text{$
\boxed{a_n=a\cdot
\left(
\frac{1}{3}\right)^{n-1}}
$}}$$

$$s_6=9+3+1+\frac{1}{3}+\frac{1}{9}+\frac{1}{27}\\ \\
s_6=13+0.\overline{481}\\\\
s_6=13.\overline{481}$$

.
 Apr 15, 2015
 #1
avatar+21978 
+5
Best Answer

Given the geometric sequence:   9,  3,  1,  ...  .      Find S6

ratio r =  $$\small{\text{$
\frac{3}{9}=\frac{1}{3} $}}$$
 and $$\small{\text{$a=9$}}$$ so

$$\small{\text{$
\boxed{a_n=a\cdot
\left(
\frac{1}{3}\right)^{n-1}}
$}}$$

$$s_6=9+3+1+\frac{1}{3}+\frac{1}{9}+\frac{1}{27}\\ \\
s_6=13+0.\overline{481}\\\\
s_6=13.\overline{481}$$

heureka Apr 15, 2015

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