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Factorising harder quadratics

Free Printable Factorising harder quadratics PDF Worksheets, Revision Guide & GCSE Past Paper Questions (Grade 7)

Download free factorising harder quadratics worksheets (PDF), GCSE maths past paper questions and worked solutions for Factorising harder quadratics (7F). This is a Grade 7 algebra topic from the GCSE questions by topic collection for Higher tier GCSE Maths (Edexcel, AQA, OCR and IGCSE).

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Free Factorising harder quadratics PDF Worksheets & Answers

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GCSE Maths Grade 7 Revision Notes & Method

Guide to Factorising harder quadratics: Explanation, Diagrams & Worked Examples

Download Printable One Page Guide (PDF)

Explanation:

To factorise a harder quadratic ax2 + bx + c (where a > 1) by splitting the middle term, multiply a × c first and find two numbers that multiply to give ac and add to give b. Rewrite the middle term bx using these two numbers, then factorise in pairs by grouping.

Always check first if there is a common numerical factor that can be taken out of all three terms, or if the expression is a difference of two squares such as 9x2 − 16y2 = (3x − 4y)(3x + 4y). If solving an equation equal to zero, set each bracket equal to zero.

Example 1: Factorise 6x2 − 11x − 10

Solution:

ac = 6 × (−10) = −60; b = −11
Numbers multiplying to −60 and adding to −11 are −15 and +4
Split middle term: 6x2 − 15x + 4x − 10
Factorise in pairs: 3x(2x − 5) + 2(2x − 5)
Answer: (3x + 2)(2x − 5)

Example 2: Solve 4x2 + 5x − 6 = 0

Solution:

ac = 4 × (−6) = −24; factors adding to +5 are +8 and −3
4x2 + 8x − 3x − 6 = 0
4x(x + 2) − 3(x + 2) = 0 ⇒ (4x − 3)(x + 2) = 0
Set each bracket to 0: 4x − 3 = 0 or x + 2 = 0
Answer: x = 34 or x = −2
Scanned GCSE Exam Questions & Worked Solutions

GCSE Past Paper Factorising harder quadratics Questions & Answers

Past Paper Example 1 IGCSE Jun 2022 1H Q11 5 marks
(a) Factorise 9x² – 4y². (2) (b) Express 7/8 – (x + 3)/(4x) as a single fraction in simplest form. (3)
(a) Factorise 9x2 - 4y2 [2 marks]
(b) Express 78 - x + 34x as a single fraction in its simplest form. [3 marks]
Worked Solution & Mark Scheme (5 marks)
Part (a) Solution:
(3x)² – (2y)² = (3x + 2y)(3x – 2y) M1 A1
Answer (a): (3x + 2y)(3x - 2y)
Part (b) Solution:
7x/(8x) – 2(x + 3)/(8x) = (7x – 2x – 6)/(8x) = (5x – 6)/(8x) M2 A1
Answer (b): 5x - 68x
Past Paper Example 2 GCSE Nov 2017 2F Q24 5 marks
(a) Solve 2x² = 72. (2) (b) Expand and simplify (2x + 1)(3x – 2). (2) (c) Factorise x² + 6x + 9. (1)
(a) Solve 2x2 = 72 [2 marks]
(b) Expand and simplify (2x + 1)(3x - 2) [2 marks]
(c) Factorise x2 + 6x + 9 [1 mark]
Worked Solution & Mark Scheme (5 marks)
Part (a) Solution:
x² = 36 M1
⇒ x = ±6 A1
Answer (a): ± 6 (or 6, -6)
Part (b) Solution:
6x² – 4x + 3x – 2 = 6x² – x – 2 M1 A1
Answer (b): 6x2 - x - 2
Part (c) Solution:
(x + 3)(x + 3) = (x + 3)² B1
Answer (c): (x + 3)2
Past Paper Example 3 AQA Nov 2024 3H Q20 2 marks
Factorise fully 3x2 + 23x + 30
Worked Solution & Mark Scheme (2 marks)
3x² + 18x + 5x + 30 = 3x(x + 6) + 5(x + 6) = (3x + 5)(x + 6). M1 A1
Answer: Answer (3x + 5)(x + 6)

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