Question

Find the 7th partial sum of ...

Answer 1

\[\sum_{i=1}^{\infty} 6(3) (^i-^1)\]

Answer 2

the exponent is i-1 I accidentally put an underscore

Answer 3

can you help me? @xxferrocixx

Answer 4

I don't know this. :O

Answer 5

@ganeshie8 @thomaster @Hero

Answer 6

it's okay, thanks anyways! @jcpd910

Answer 7

\[
\sum_{i=1}^\infty 6(3)^{i-1}
\]

Answer 8

This is a geometric series.

Answer 9

When \[a_n = ar^{n-1}
\]Then \[
S_n = \frac{1-r^n}{1-r}
\]

Answer 10

Where \(S_n\) is the \(n\)th partial sum: \(S_n = \sum_{i=1}^na_i\)

Answer 11

\[
\sum_{i=1}^\infty \color{blue}{6}(\color{red}{3})^{i-1}
\]\[
a_n =\color{blue}{a}(\color{red}{r})^{n-1}
\]

Answer 12

okay, I get it now. Thank you so much!

Answer 13

I need to make a correction:

When \[a_n = ar^{n-1}
\]Then \[
S_n =a\left( \frac{1-r^n}{1-r}\right)
\]

Answer 14

thank you!