What do I need to know about rationalising denominators?
- Rationalising a denominator changes a fraction with surds in its denominator, into an equivalent fraction where the denominator is a rational number (usually an integer) and any surds are in the numerator
- There are three cases you need to know how to deal with when rationalising denominators:
Exam Tip
- If an exam question asks you to give an answer, for example, "in the form p + q√3 , where p and q are rational numbers", this does NOT mean that p and q have to be integers, or positive!
- Remember: both integers and fractions (both positive and negative) are rational numbers.
Worked Example
