\(B^2=4+\sqrt{10+2\sqrt{5}}+4-\sqrt{10+2\sqrt{5}}+2\cdot\sqrt{16-10-2\sqrt{5}}\)
\(=8+2\cdot\sqrt{6-2\sqrt{5}}\)
\(=8+2\sqrt{5}-2=6+2\sqrt{5}\)
Do đó: \(B=\sqrt{5}+1\)
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