[tex]A=\sqrt{4-\sqrt{15}}-\sqrt{4+\sqrt{15}}+\sqrt{6} A\sqrt{2}=\sqrt{8-2\sqrt{15}}-\sqrt{8+2\sqrt{15}}+\sqrt{12} =\sqrt{(\sqrt{5}-\sqrt{3})^{2}}-\sqrt{(\sqrt{5}+\sqrt{3})^{2}}+\sqrt{12} =\sqrt{5}-\sqrt{3}-\sqrt{5}-\sqrt{3}+\sqrt{12} = -2\sqrt{3}+2\sqrt{3}=0[/tex]