$9$

$(10)$ Determine whether the series is convergent or divergent. If it is convergent, find its sum.

${\displaystyle \underset{i=1}{\overset{}{}}}\frac{(-5{)}^n}{6^{n+1}}$

$(11)$ Express the number as a ratio of integers: $\frac{3.}{b}ar(4)6=3\mathrm{.}46464646$dots