\[\left( \sqrt{7 - 4\sqrt{3}} + \sqrt{7 + 4\sqrt{3}} \right)^{2} =\]
\[= 14 + 2\sqrt{7^{2} - \left( 4\sqrt{3} \right)^{2}} =\]
\[= 14 + 2\sqrt{49 - 16 \cdot 3} =\]
\[= 14 + 2\sqrt{49 - 48} =\]
\[= 14 + 2\sqrt{1} = 14 + 2 = 16\]