Выполните действия: 1/(ab)^2:an/b^2.

\[\frac{1}{\left( \text{ab} \right)^{2}}\ :\frac{\text{an}}{b^{2}} = \frac{b^{2}}{a^{2}b^{2} \cdot an} = \frac{1}{a^{3}n}.\]