# \sum_{k=1}^{x} \frac{k+5}{5^{k}} \text { 6b..) } \sum_{n=1}^{x} \frac{3^{n} n^{2}}{n !} \sum_{n=3}^{x} \frac{3 n+5}{n(n-1)(n-2)} \text { 6d.) } \sum_{n=3}^{x} \frac{e^{n}+n}{e^{2 n}-n^{2}} 7.) Determine if the series converges absolutely, conditionally, \text {

a.) } \sum_{n=1}^{x} \frac{(-1)^{n}}{1+1 / n} \text { b.) } \sum_{n=1}^{x} \frac{\cos 1 / n}{n^{2}}