0. Review

Rationalize the denominator. 

$-\frac{5}{2\sqrt{7}}$

Rationalize the denominator.

$\frac{6+\sqrt{x}}{-\sqrt{x}}$

Rationalize the denominator and simplify the radical expression.

$\frac{\sqrt{7}}{5-\sqrt{6}}$

Rationalize the denominator and simplify the radical expression.

$\frac{2-\sqrt{3}}{2+\sqrt{3}}$