Mathematics

Problem

Which of the following series diverges based solely on the behavior of its

n

th term? a)

\displaystyle \sum_{n=1}^{\infty}\frac{1}{\sqrt n}

\displaystyle \sum_{n=1}^{\infty}\frac{(-1)^n}{n}

\displaystyle \sum_{n=1}^{\infty}\frac{n+1}{2n}

\displaystyle \sum_{n=1}^{\infty}\frac{1}{n}