[tex]\displaystyle\\\sqrt{3,6}\times\sqrt{6,4}=\\ \\=\sqrt{3,6\times\frac{10}{10}} \times\sqrt{6,4\times\frac{10}{10}}=\\\\\text{Am inmultit numarul de sub fiecare radical cu }~\frac{10}{10}\\\\\text{Rezultatul nu se schimba deoarece }~\frac{10}{10}=1\\\\=\sqrt{\frac{3,6\times10}{10}} \times\sqrt{\frac{6,4\times10}{10}}=\\\\=\sqrt{\frac{36}{10}} \times\sqrt{\frac{64}{10}}=\\\\\frac{6}{\sqrt{10}}\times\frac{8}{\sqrt{10}}}=\frac{48}{10}=\boxed{\bf4,\!8}[/tex]
