a: \(A^2=12-2\sqrt{7}+12+2\sqrt{7}-2\cdot\sqrt{116}\)
\(\Leftrightarrow A^2=24-4\sqrt{29}\)
hay \(A=\sqrt{24-4\sqrt{29}}\)
c: \(C=\dfrac{\sqrt{6-2\sqrt{5}}+\sqrt{6+2\sqrt{5}}}{\sqrt{2}}\)
\(=\dfrac{\sqrt{5}-1+\sqrt{5}+1}{\sqrt{2}}=\dfrac{2\sqrt{5}}{\sqrt{2}}=\sqrt{10}\)