\(A=\sqrt{3-\sqrt{5}}-\sqrt{4-\sqrt{15}}+\sqrt{6-3\sqrt{3}}\)
\(=\dfrac{1}{\sqrt{2}}\cdot\left(\sqrt{6-2\sqrt{5}}-\sqrt{8-2\sqrt{15}}+\sqrt{12-6\sqrt{3}}\right)\)
\(=\dfrac{1}{\sqrt{2}}\left(\sqrt{5}-1-\sqrt{5}+\sqrt{3}+3-\sqrt{3}\right)\)
=2/căn 2=căn 2
\(B=\sqrt{4-\sqrt{7}}-\sqrt{14-5\sqrt{3}}-\sqrt{5+\sqrt{21}}\)
\(=\dfrac{1}{\sqrt{2}}\left(\sqrt{8-2\sqrt{7}}-\sqrt{28-10\sqrt{3}}-\sqrt{10+2\sqrt{21}}\right)\)
\(=\dfrac{1}{\sqrt{2}}\left(\sqrt{7}-1-5+\sqrt{3}-\sqrt{7}-\sqrt{3}\right)\)
=-6/căn 2=-3căn2
\(C=\sqrt{11-6\sqrt{2}}-\sqrt{6-4\sqrt{2}}+\sqrt{7-2\sqrt{6}}\)
=3-căn 2-2+căn 2+căn 6-1
=căn 6
\(D=\sqrt{6-\sqrt{11}}-\sqrt{10+3\sqrt{11}}+2\sqrt{2}-1\)
\(=\dfrac{1}{\sqrt{2}}\left(\sqrt{12-2\sqrt{11}}-\sqrt{20+6\sqrt{11}}\right)+2\sqrt{2}-1\)
\(=\dfrac{1}{\sqrt{2}}\left(\sqrt{11}-1-\sqrt{11}-3\right)+2\sqrt{2}-1\)
=-1
\(F=\sqrt{6+3\sqrt{3}}-\sqrt{2+\sqrt{3}}+\sqrt{6-4\sqrt{2}}\)
\(=\dfrac{1}{\sqrt{2}}\left(\sqrt{12+6\sqrt{3}}-\sqrt{4+2\sqrt{3}}\right)+2-\sqrt{2}\)
=1/căn 2(3+căn 3-căn 3-1)+2-căn 2
=căn 2+2-căn 2
=2
cảm ơn 
