Grade 11 · Theory
Solving by factorising and the formula
Quadratics · about 3 min
Visual overview: Solving by factorising and the formula1 MIN READ
2 study sections · pause after each one and recall the key ideaGrade 11 completes your quadratic toolkit: when factorising fails, the quadratic formula always works.
Key points- Standard form first: ax² + bx + c = 0.
- Factorise when you can — it is faster and less error-prone.
- Otherwise x = [−b ± √(b² − 4ac)] / 2a.
- Substitute a, b and c carefully with their signs, especially a negative b.
- Quadratic formula — the general solution for any quadratic.
EXAM TIP
write the formula down before substituting; you earn a mark for the correct formula even if the arithmetic slips.