Evaluate the integral by completing the square and using trigonometric substitution.

${\displaystyle \underset{\phantom{}}{\overset{\phantom{}}{}}}\sqrt[\phantom{2}]{x^2}-4x-45dx$

$($Express numbers in exact form. Use symbolic notation and fractions where needed. Use $C$ fo into $C$ as much as possible.$)$

${\displaystyle \underset{\phantom{}}{\overset{\phantom{}}{}}}\sqrt[x]{x^2-4x-45}dx=$