Bonjour !
a)
[tex]\frac{2}{\sqrt{3}} = \frac{2\sqrt{3}}{\sqrt{3}*\sqrt{3}} = \frac{2\sqrt{3}}{3}[/tex]
b)
[tex]\frac{7}{2\sqrt{5}} = \frac{7\sqrt{5}}{2\sqrt{5}*\sqrt{5}} = \frac{7\sqrt{5}}{2*5} = \frac{7\sqrt{5}}{10}[/tex]
c)
[tex]\frac{\sqrt{3}}{4\sqrt{2}} = \frac{\sqrt{3}*\sqrt{2}}{4\sqrt{2}*\sqrt{2}} = \frac{\sqrt{6}}{4*2} = \frac{\sqrt{6}}{8}[/tex]
d)
[tex]\frac{3\sqrt{3}}{\sqrt{8}} = \frac{3\sqrt{3}*\sqrt{2}}{\sqrt{8}*\sqrt{2}} = \frac{3\sqrt{6}}{\sqrt{16}} = \frac{3\sqrt{6}}{4}[/tex]
Voilà !
