Solving by factorising and the formula

Grade 11 completes your quadratic toolkit: when factorising fails, the quadratic formula always works.

• 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.