#### Revision Notes

##### What is a quadratic expression?

A quadratic expression looks like this:

ax2 + bx + c (as long as a ≠ 0)

Note: If there are any higher powers of x (like x3 say) then it is not a quadratic!

##### Factorising a 3-term quadratic expression (a = 1)

1. Signs in quadratic determine signs in brackets:
• if c is positive then both signs are the same as the sign of b
• if c is negative then the signs are different and bigger number has the sign of b
2. Using those signs find numbers p and q which
• multiply to give c
3. Write down the brackets (x + p)(x + q) – that’s your answer!
Don’t forget – both p and q here can be negative!

## Want to aim for a Level 9?

See if you’ve got what it takes. Test yourself with our topic questions.

### Author: Simon

After 24 years teaching A Level Further Maths, Maths whizz Simon focused his attention on tutoring. He’s helped thousands of young people make sense of Maths and now he’s helping you too – aren’t you lucky! He’s even worked as an Edexcel examiner, so knows exactly what they’re looking for.