Because we have .
Do you see that ?
This means that
I posted this one over a week ago, but was hoping that someone might have some input on it.
a. Show that if an > 0, and lim(n*an) = q with q not equal to zero, then the series Σan diverges.
b. Assume an > 0 and lim(n^2 * an) exists. Show that Σan converges.