Grade five, CIE IGCSE Maths

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
    • add to give b
  3. Write down the brackets (x + p)(x + q) – that’s your answer!
    Don’t forget – both p and q here can be negative!


Factorising Quadratics - Basic Example, IGCSE & GCSE Maths revision notes


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