Solution
= Solution
The <telescoping series> has partial sum $S_N=w_{N+1}-w_1$. Therefore the necessary and sufficient condition is \b[that $w_n$ have a finite limit] $L$. The sum is then $L-w_1$.
= Solution
The <telescoping series> has partial sum $S_N=w_{N+1}-w_1$. Therefore the necessary and sufficient condition is \b[that $w_n$ have a finite limit] $L$. The sum is then $L-w_1$.