\[\frac{1}{\sqrt{5 + \sqrt{12}} - 1} - \frac{1}{\sqrt{5 + \sqrt{12}} + 1} =\]
\[= \frac{2}{4 + \sqrt{12}} = \frac{2}{4 + 2\sqrt{3}} =\]
\[= \frac{2 - \sqrt{3}}{\left( 2 + \sqrt{3} \right)\left( 2 - \sqrt{3} \right)} = \frac{2 - \sqrt{3}}{4 - 3} =\]
\[= \frac{2 - \sqrt{3}}{1} = 2 - \sqrt{3}\]