CPM Homework Help : PC3 Problem 6-56

Solve each of the following equations. Use $u$ -substitution to make the process easier.

$\frac { 12 } { \sqrt { x ^ { 2 } + 5 } } + \sqrt { x ^ { 2 } + 5 } = 7$
Hint (b):
Let $u=\sqrt{x^{2}+5}$ .