For x² + bx + c, find two numbers that:
MULTIPLY to give c
ADD to give b
Example: x² + 5x + 6
- Need: multiply to 6, add to 5
- Numbers: 2 and 3 (2×3=6, 2+3=5)
- Answer: (x + 2)(x + 3)
This key facts covers The "Two Numbers" Method within Factorising for GCSE Mathematics. Revise Factorising in Algebra for GCSE Mathematics with 12 exam-style questions and 3 flashcards. This topic appears regularly enough that it should still be part of a steady revision cycle. It is section 9 of 13 in this topic. Use this key facts to connect the idea to the wider topic before moving on to questions and flashcards.
Practice questions for Factorising
Which is the correct factorisation of 6x + 15?
A student factorises x² + 5x + 4 as (x + 4)(x + 4). Explain why this is incorrect and give the correct factorisation.
Quick recall flashcards
Factorising
Take out highest common factor: 6x + 9 = 3(2x + 3)
Factorising Rule
Find the HCF of all terms (numbers AND letters), put outside bracket, divide each term for inside.