Slippery Sum!
Calculus
Level
4
\[ \displaystyle\sum _{ r=1 }^{ \infty }{ \frac { r\left( r+1 \right) }{ { 3 }^{ r } } } \]
If the summation above equals to \( \frac m n \) for coprime positive integers \(m,n\), what is the value of \(m+n\)?
by
Atul Antony Zachariahs