MEPX
Chapter 3 of 10All chapters
  1. 1Why letters
  2. 2Rearranging
  3. 3Expanding and factorising
  4. 4Straight lines
  5. 5Quadratics
  6. 6Fractions and powers
  7. 7Two unknowns
  8. 8Inequalities
  9. 9Functions
  10. 10Turning words into algebra

Chapter 3 of 10

Expanding and factorising

The same move in both directions.

Expanding

Multiply every term in one bracket by every term in the other, then collect like terms. (x + 3)(x + 2) becomes x squared + 5x + 6.

  • The middle coefficient is the sum, the last term is the product.
  • Watch signs: a minus inside a bracket flips everything it multiplies.

Factorising

Going backwards means finding two numbers that multiply to the constant and add to the middle coefficient. It is the standard route to solving a quadratic by hand.