\[(x + 2)\sqrt{x^{2} - 9} = 0\]
\[x + 2 = 0\]
\[\ x = - 2.\]
\[\sqrt{x^{2} - 9} = 0\]
\[x^{2} - 9 = 0\ \ \]
\[x^{2} = 9\ \ \]
\[x = \pm 3.\]