Please give me the help to find out the divergence or convergence of attached picture here:
Thanks
I think all the sums from 1 to $\displaystyle \infty$.
problem (a)(ii)
using the ratio test,
$\displaystyle \rho=\lim\limits_{n\longrightarrow\infty}\frac{a_{ n+1}}{a_{n}}=\lim
\limits_{n\longrightarrow\infty}\frac{4}{n+1}=0<1$
hence, this series converge.