1) \(2\left(\sqrt{10}-\sqrt{2}\right).\sqrt{4+\sqrt{6-2\sqrt{5}}}=2\left(\sqrt{10}-\sqrt{2}\right).\sqrt{4+\sqrt{\left(\sqrt{5}-1\right)^2}}\)
\(=2\left(\sqrt{10}-\sqrt{2}\right).\sqrt{3+\sqrt{5}}=2\left(\sqrt{30+10\sqrt{5}}-\sqrt{6+2\sqrt{5}}\right)\)
\(=2\left(\sqrt{\left(5+\sqrt{5}\right)^2}-\sqrt{\left(\sqrt{5}+1\right)^2}\right)=2\left(5+\sqrt{5}-\left(\sqrt{5}+1\right)\right)\) \(=2\left(5+\sqrt{5}-\sqrt{5}-1\right)=2.4=8\)
2) \(\left(4\sqrt{2}+\sqrt{30}\right)\left(\sqrt{5}-\sqrt{3}\right)\sqrt{4-\sqrt{15}}\)
\(=\left(4\sqrt{10}-4\sqrt{6}+5\sqrt{6}-3\sqrt{10}\right)\sqrt{4-\sqrt{15}}\)
\(=\left(\sqrt{10}+\sqrt{6}\right)\sqrt{4-\sqrt{15}}=\sqrt{40-10\sqrt{15}}+\sqrt{24-6\sqrt{15}}\)
\(=\sqrt{\left(5-\sqrt{15}\right)^2}+\sqrt{\left(\sqrt{15}-3\right)^2}=5-\sqrt{15}+\sqrt{15}-3=2\)
3) \(\left(\sqrt{21}+7\right)\sqrt{10-2\sqrt{21}}=\left(\sqrt{21}+7\right)\sqrt{\left(\sqrt{7}-\sqrt{3}\right)^2}\)
\(\left(\sqrt{21}+7\right)\left(\sqrt{7}-\sqrt{3}\right)=7\sqrt{3}-3\sqrt{7}+7\sqrt{7}-7\sqrt{3}=4\sqrt{7}\)
