Basic rules

A surd is a square root which cannot be reduced to a whole number. For example, is not a surd, as the answer is a whole number. But is not a whole number. You could use a calculator to find that but instead of this we often leave our answers in the square root form, as a surd.

You need to be able to simplify expressions involving surds. Here are some general rules that you will need to learn.

Now have a look at some questions.

Rationalising

Rationalising an expression means getting rid of any surds from the bottom of fractions. Usually when you are asked to simplify an expression it means you should also rationalise it.