Evaluate ${\displaystyle \underset{\phantom{}}{\overset{\phantom{}}{}}}\frac{1}{x^3\sqrt[\phantom{2}]{x^2-9}}dx$

$\frac{1}{18}co{s}^{-1}(\frac{3}{x})\frac{\sqrt[\phantom{2}]{x^2-9}}{6x^2}c$

$\frac{1}{54}co{s}^{-1}(\frac{3}{x})-\frac{\sqrt[\phantom{2}]{x^2-9}}{18x^2}c$

$co{s}^{-1}(\frac{18}{x})\frac{\sqrt[\phantom{2}]{x^2-9}}{18x^2}c$

$\frac{1}{54}co{s}^{-1}(\frac{3}{x})\frac{\sqrt[\phantom{2}]{x^2-9}}{18x^2}c$