Question

Number 13 please show me in the least steps possible

Answer 1

$\frac{\sqrt3}{-\sqrt21}=\\ -\frac{\sqrt{63}}{21}=\\ -\frac{3\sqrt7}{21}=\\ -\frac{\sqrt7}{7}$

Answer 2

$\frac{\sqrt3}{-\sqrt{21}}=-\sqrt\frac{3}{21}=-\sqrt\frac{1}{7}=-\frac{\sqrt1}{\sqrt7}=-\frac{1}{\sqrt7}=-\frac{1}{\sqrt7}\times\frac{\sqrt7}{\sqrt7}=-\frac{\sqrt7}{7}$