Evaluate the following integral using trigonometric substitution.

${\displaystyle \underset{\phantom{}}{\overset{\phantom{}}{}}}\frac{dx}{x(x^2-81{)}^{\frac{3}{2}}},x>9$

${\displaystyle \underset{\phantom{}}{\overset{\phantom{}}{}}}\frac{dx}{x(x^2-81{)}^{\frac{3}{2}}}=$

$($Type an exact answer.$)$