- Sign errors: (x - 3)(x + 2) ≠ x² + x - 6
Correct: x² - x - 6 (careful with the middle term!) - Forgetting the x² term: Always check your first term is x²
- Wrong factor pairs: For x² + 7x + 10, don't use (x + 1)(x + 10)
Check: 1 + 10 = 11 ≠ 7 - Perfect square confusion: (x + 3)² ≠ x² + 9
Correct: (x + 3)² = x² + 6x + 9 - Missing negative signs: When one factor is negative, be extra careful with signs throughout
This exam tips covers Common Mistakes to Avoid within Quadratic Expressions for GCSE Mathematics. Revise Quadratic Expressions in Algebra for GCSE Mathematics with 12 exam-style questions and 22 flashcards. This topic appears regularly enough that it should still be part of a steady revision cycle. It is section 7 of 8 in this topic. Treat this as a marking guide for what examiners are looking for, not just a fact list.
Practice questions for Quadratic Expressions
Expand (x + 5)².
Explain how to recognise whether x² + 12x + 36 is a perfect square trinomial, and write it in factorised form.
Quick recall flashcards
Expand (x + 2)(x + 5)
x² + 5x + 2x + 10
= x² + 7x + 10
(Using FOIL: First + Outer + Inner + Last)
Expand (x + 6)(x - 4)
x² - 4x + 6x - 24
= x² + 2x - 24
(Be careful with negative signs!)