Lời giải:
Đặt \(A=\sqrt{6+3\sqrt{3}}+\sqrt{6-3\sqrt{3}}\)
\(\Rightarrow A\sqrt{2}=\sqrt{12+6\sqrt{3}}+\sqrt{12-6\sqrt{3}}\)
\(A\sqrt{2}=\sqrt{3^2+3-2.3\sqrt{3}}+\sqrt{3^2+3-2.3\sqrt{3}}\)
\(=\sqrt{(3+\sqrt{3})^2}+\sqrt{(3-\sqrt{3})^2}\)
\(=3+\sqrt{3}+3-\sqrt{3}=6\)
\(\Rightarrow A=\frac{6}{\sqrt{2}}=3\sqrt{2}\)