A friend of mine (and now I am) is trying to solve this for a high school kid's AP calculus course. I'm not really worried about the limit part but more how you work it into the correct form to get arctan as an answer. Wolfram took away their free step by step solutions and I'm out of tricks of my own.

$\displaystyle \int_{-\infty }^{\infty }\frac{dx}{(64+x)\sqrt{x}}$

Thanks in advance!