$\frac{1}{1},-\frac{1}{8},\frac{1}{27},$dots

Use symbolic notation and fractions where needed.$)$

$a_n=$

$$

Find a formula $b_n$ for the $n-$th term of the following sequence. Assume the series begins at $n=1.$

$\frac{4}{6},\frac{5}{7},\frac{6}{8},$dots

$($Use symbolic notation and fractions where needed.$)$

Question Source: Rogaester te Caloula