How do you use the difference of two squares formula to factor 1/81 - n^2 ?

$\frac{1}{81} - {n}^{2}$
$= \left({\left(\frac{1}{9}\right)}^{2} - {n}^{2}\right)$
$= \left(\frac{1}{9} - n\right) \left(\frac{1}{9} + n\right)$