Đặt \(A=\sqrt{10-6\sqrt{2}}-\sqrt{10+6\sqrt{2}}\)
=>A2=\(20-2\sqrt{10^2-\left(6\sqrt{2}\right)^2}\)
=\(20-4\sqrt{7}\Rightarrow A=-\sqrt{20-4\sqrt{7}}\left(\text{Vì ta dễ thấy }A< 0\right)\)
Tới đó là hết gọn dc r v~
\(\sqrt{10-6\sqrt{2}}-\sqrt{10+6\sqrt{2}}\)
=\(\sqrt{\left(\sqrt{5+\sqrt{7}}-\sqrt{5-\sqrt{7}}\right)^2}-\sqrt{\left(\sqrt{5+\sqrt{7}}+\sqrt{5-\sqrt{7}}\right)^2}\)
=\(\sqrt{5+\sqrt{7}}-\sqrt{5-\sqrt{7}}-\sqrt{5+\sqrt{7}}-\sqrt{5-\sqrt{7}}\)
=\(-2\sqrt{5-\sqrt{7}}\)