[tex]a)\\\frac4{\sqrt5}=\frac4{\sqrt5}*\frac{\sqrt5}{\sqrt5}=\frac{4\sqrt5}5\\b)\\\frac6{\sqrt{12}}=\frac6{\sqrt{12}}*\frac{\sqrt{12}}{\sqrt{12}}=\frac{6\sqrt{12}}{12}=\frac{\sqrt{12}}2\\c)\\\frac{20}{\sqrt{10}}=\frac{20}{\sqrt{10}}*\frac{\sqrt{10}}{\sqrt{10}}=\frac{20\sqrt{10}}{10}=2\sqrt{10}\\d)\\\frac3{4\sqrt3}=\frac3{4\sqrt3}*\frac{\sqrt3}{\sqrt3}=\frac{3\sqrt3}{4*3}=\frac{3\sqrt3}{12}=\frac{\sqrt3}4[/tex]
