3: 1/7*căn 245=1/7*7căn 5=căn 5
1/9*căn 486=1/9*9căn 6=căn 6
=> <
5: \(\sqrt{4\sqrt{2}+2\sqrt{6}}=\sqrt{2\left(2\sqrt{2}+\sqrt{6}\right)}=\sqrt{\sqrt{2}\left(4+2\sqrt{3}\right)}\)
\(=\sqrt{\sqrt{2}}\left(\sqrt{3}+1\right)\)
2: 12/căn 5=12/5*căn 5
căn 5*căn 25=5 căn 5
=> <