Surds

Literally everything for IGCSE maths (higher tier, Edexcel)

Oh, we're doing the same exam board at least from what I've seen Edexcel IGCSE surds questions are just about applying rules. The most important one is probably $\sqrt{ab} = \sqrt{a} * \sqrt{b}$ (e.g. $\sqrt{27} = \sqrt{3} * \sqrt{9} = 3\sqrt{3}$) since you can usually use that rule to simplify surds, which comes up on its own and as part of expanding brackets/proof-like surd questions. The other thing that comes up is rationalising the denominator, which is basically just multiplying it such that the denominator gets squared/cancelled-out and thus becomes rational. For example, if your fraction were $\frac{7}{\sqrt{2}}$ you would multiply it by $\frac{\sqrt{2}}{\sqrt{2}}$ so that the denominator gets squared and becomes 2. If you had a denominator like $3 + \sqrt{2}$ containing a rational number, you would have to multiply it by $3 - \sqrt{2}$, switching the signs in the same way as you would in a difference of two squares equation.

Does that help? If there's anything more specific or a certain question you're having trouble with, let me know.