Use the fact that if a series ∑ n = 0 ∞ b n {\displaystyle \sum _{n=0}^{\infty }b_{n}} converges, then lim n → ∞ b n = 0. {\displaystyle \lim _{n\rightarrow \infty }b_{n}=0.}
Equivalently, if lim n → ∞ b n ≠ 0 {\displaystyle \lim _{n\rightarrow \infty }b_{n}\neq 0} , then the series ∑ n = 0 ∞ b n {\displaystyle \sum _{n=0}^{\infty }b_{n}} diverges.
