\[a > - 2:\ \]
\[(a + 2)\sqrt{\frac{2}{a^{2} + 4a + 4}} =\]
\[= \ (a + 2)\sqrt{\frac{2}{(a + 2)^{2}}} =\]
\[= \frac{(a + 2)}{(a + 2)}\sqrt{2} = \sqrt{2}.\]