Trả lời:
\(\left(2\sqrt{2}-\sqrt{5}+3\sqrt{2}\right).\left(\sqrt{18}-\sqrt{20}+2\sqrt{2}\right)\)
\(=\left(5\sqrt{2}-\sqrt{5}\right).\left(3\sqrt{2}-2\sqrt{5}+2\sqrt{2}\right)\)
\(=\left(5\sqrt{2}-\sqrt{5}\right).\left(5\sqrt{2}-2\sqrt{5}\right)\)
\(=50-10\sqrt{10}-5\sqrt{10}+10\)
\(=60-15\sqrt{10}\)