Given
Series,
[tex]27,9,3,1,\frac{1}{3},\frac{1}{9},...[/tex]Find
Write the sigma notation for the infinite series.
Explanation
as we see the given series is a geometric series .
here , a = 27
common ratio , r = 9/27 = 1/3
so ,
[tex]\begin{gathered} \sum_{n\mathop{=}1}^{\infty}ar^{n-1} \\ \\ \sum_{n\mathop{=}1}^{\infty}(27)(\frac{1}{3})^{n-1} \\ \\ \sum_{n\mathop{=}1}^{\infty}(\frac{1}{3})^{-3}(\frac{1}{3})^{n-1} \\ \\ \sum_{n\mathop{=}1}^{\infty}(\frac{1}{3})^{n-4} \end{gathered}[/tex]Final Answer
Hence , the sigma notation for the infinite series is
[tex]\sum_{n\mathop{=}1}^{\infty}(\frac{1}{3})^{n-4}[/tex]