\[\left( \sqrt{8 + 2\sqrt{7}} + \sqrt{8 - 2\sqrt{7}} \right)^{2} =\]
\[= 16 + 2\sqrt{64 - 28} =\]
\[= 16 + 2\sqrt{36} = 16 + 2 \cdot 6 =\]
\[= 16 + 12 = 28\]