Sagot :
[tex]\frac{\sqrt3}{-\sqrt{21}}=-\sqrt\frac{3}{21}=-\sqrt\frac{1}{7}=-\frac{\sqrt1}{\sqrt7}=-\frac{1}{\sqrt7}=-\frac{1}{\sqrt7}\times\frac{\sqrt7}{\sqrt7}=-\frac{\sqrt7}{7}[/tex]
[tex]\frac{\sqrt3}{-\sqrt21}=\\ -\frac{\sqrt{63}}{21}=\\
-\frac{3\sqrt7}{21}=\\
-\frac{\sqrt7}{7}[/tex]