Question

giúp với ạ

Answer 1

Đặt \(A=\sqrt{4+\sqrt{10+2\sqrt{5}}}+\sqrt{4-\sqrt{10+2\sqrt{5}}}\)

\(A^2=8+2\sqrt{6-2\sqrt{5}}=8+2\left|\sqrt{5}-1\right|=6+2\sqrt{5}\)

\(A=\sqrt{A^2}=\sqrt{6+2\sqrt{5}}=\left|\sqrt{5}+1\right|=\sqrt{5}+1\)