Rationalise the denominator in each of the following:
$\frac{5-2 \sqrt{6}}{5+2 \sqrt{6}}$

(A) To rationalise the denominator,multiply the numerator and the denominator by the conjugate of the denominator,which is $(5-2 \sqrt{6})$.
$\frac{5-2 \sqrt{6}}{5+2 \sqrt{6}} \times \frac{5-2 \sqrt{6}}{5-2 \sqrt{6}}$
$= \frac{(5-2 \sqrt{6})^2}{(5)^2 - (2 \sqrt{6})^2}$
$= \frac{5^2 - 2(5)(2 \sqrt{6}) + (2 \sqrt{6})^2}{25 - (4 \times 6)}$
$= \frac{25 - 20 \sqrt{6} + 24}{25 - 24}$
$= \frac{49 - 20 \sqrt{6}}{1}$
$= 49 - 20 \sqrt{6}$