Question

Write the lowest rationalising factor of:-
$\sqrt{5} - 3$
​

Answer 1

$\sqrt{5} + 3$

Is the lowest rationalising factor of $\sqrt{5} - 3$ As,

$( \sqrt{5} - 3)( \sqrt{5} + 3) \\ = \sqrt{5} ^{2} - {3}^{2} \\ = 5 - 9 = -4$

which is rational.