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.
Common Mistakes to Avoid
- 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
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!)