Can someone show me exactly step by step how to rationalise the denominator in this question?
$\displaystyle \frac{1}{\sqrt{2} + \sqrt{3} + \sqrt{5}}$
You have to doe this question in (at least) 2 steps:
$\displaystyle \dfrac{1}{\sqrt{2} + \sqrt{3} + \sqrt{5}}\cdot \dfrac{(\sqrt{2} + \sqrt{3})- \sqrt{5}}{(\sqrt{2} + \sqrt{3})- \sqrt{5}}=\dfrac{\sqrt{2} + \sqrt{3} - \sqrt{5}}{2\sqrt{6}}$
I'll leave the 2nd step for you.