Identity. A statement that is TRUE for ALL values of the variable. Often written with ≡.
Examples:
(a+b)2≡a2+2ab+b2 (always true).
sin2θ+cos2θ≡1 (always true).
a(b+c)≡ab+ac (distributive identity).
Worked qualitative. Is x2=16 an equation or identity?
True only for x=4 or x=−4, not for ALL x.
It's an EQUATION.
Worked qualitative. Is (a+b)2=a2+b2 an identity?
(1+2)2=9, but 12+22=5. Different.
NOT true for all values.
NOT an identity. (And, as a matter of fact, it's never true except when a=0 or b=0.)
Edexcel tip. Sometimes Edexcel asks 'Show that ... is an identity'. You need to prove it works for ALL values, usually by expanding both sides until they're equal.
Expression: simplify only.
Equation: solve.
Identity: always true; prove by expanding.
= for equations, ≡ for identities.
How it’s examined
Algebraic manipulation appears every Paper 1H AND 2H, often as the first 2-4 marks of an algebra question, but also as multi-step questions for 4-6 marks. Examiner reports flag (1) writing (a+b)2 as a2+b2, (2) sign errors with negative brackets, (3) combining unlike terms.
Worked examples, formulae, definitions and the mistakes examiners flag — everything you need to push from a pass to an A*.
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Step-by-step worked examples — Algebraic Manipulation
Step-by-step solutions to past-paper-style questions on algebraic manipulation, written exactly the way a tutor would explain them at the board.
1Expand a single bracket
Foundation• expand
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Question
Expand 3x(2x2−5x+4).
Step-by-step solution
Step 1
Multiply each term in the bracket by 3x.
3x⋅2x2=6x3,3x⋅(−5x)=−15x2,3x⋅4=12x
Step 2
Combine:
3x(2x2−5x+4)=6x3−15x2+12x
Answer
6x3−15x2+12x
Examiner tip
Use the index laws when multiplying: 3x⋅2x2=6x3 (multiply numbers, ADD indices). Mark schemes deduct for indexing errors.
2Expand a double bracket
Foundation• Adapted from 4MA1/1H May/Jun 2024 Q5• expand, FOIL
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Question
Expand and simplify (2x+3)(x−4).
Step-by-step solution
Step 1
Use FOIL: First, Outer, Inner, Last.
(2x)(x)+(2x)(−4)+(3)(x)+(3)(−4)
Step 2
Compute each: 2x2−8x+3x−12.
Step 3
Combine like terms: 2x2−5x−12.
Answer
2x2−5x−12
Examiner tip
Show every FOIL step. Mark scheme awards M1 for any 3 of 4 terms correct, A1 for the simplified answer.
3Square a binomial
Higher• expand, squaring
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Question
Expand (3x−2)2.
Step-by-step solution
Step 1
(a−b)2=a2−2ab+b2.
Step 2
a=3x, b=2. Substitute:
(3x)2−2(3x)(2)+22=9x2−12x+4
Answer
9x2−12x+4
Examiner tip
Common error: writing (3x−2)2 as 9x2−4 (missing middle term). The expansion has THREE terms, not two.
4Expand three brackets
Higher• Adapted from 4MA1/2H Jan 2024 Q6• expand, three brackets
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Question
Expand and simplify (x+1)(x−2)(x+3).
Step-by-step solution
Step 1
Multiply the first two brackets first using FOIL: (x+1)(x−2)=x2−x−2.
Step 2
Multiply the result by (x+3):
(x2−x−2)(x+3)=x3+3x2−x2−3x−2x−6
Step 3
Simplify: x3+2x2−5x−6.
Answer
x3+2x2−5x−6
Examiner tip
Always do TWO brackets first, then expand by the third. Mark schemes credit each stage; trying all three at once invites errors.
5Simplify by collecting like terms
Foundation• simplify, like terms
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Question
Simplify 5x2−3x+7−2x2+5x−4.
Step-by-step solution
Step 1
Group like terms by power.
Step 2
x2: 5x2−2x2=3x2.
Step 3
x: −3x+5x=2x.
Step 4
Constants: 7−4=3.
Step 5
Result: 3x2+2x+3.
Answer
3x2+2x+3
Examiner tip
Like terms have the SAME variable to the SAME power. x2 and x are NOT like terms. Always sort by power before combining.
Key Formulae — Algebraic Manipulation
The formulae you need to memorise for algebraic manipulation on the Pearson Edexcel IGCSE 4MA1 paper, with every variable defined in plain English and a note on when to use it.
Difference of two squares
(a−b)(a+b)=a2−b2
a,b
any expressions
When to use
When expanding products of conjugates. Also a standard factoring pattern.
Example
(x−4)(x+4)=x2−16. (2x−3)(2x+3)=4x2−9.
Square of a binomial
(a+b)2=a2+2ab+b2
a,b
any expressions
When to use
When squaring a sum. Also (a−b)2=a2−2ab+b2 for difference.
Example
(3x+2)2=9x2+12x+4. (x−5)2=x2−10x+25.
Key Definitions and Keywords — Algebraic Manipulation
Definitions to memorise and the exact keywords mark schemes credit for algebraic manipulation answers — sharpened from recent examiner reports for the 2026 Pearson Edexcel IGCSE 4MA1 sitting.
Expression
Examiner keyword
A combination of variables, numbers, and operations — but NO equals sign.
Example
3x2+2x−5 is an expression.
Equation
Examiner keyword
A statement that two expressions are equal, using =.
Example
3x+2=11.
Identity
Examiner keyword
An equation that is TRUE for ALL values of the variable. Often written with ≡.
Example
(a+b)2≡a2+2ab+b2.
Like terms
Terms with the SAME variable raised to the SAME power. Their coefficients can be combined.
Example
3x2 and −7x2 are like terms. 3x and 3x2 are NOT.
Coefficient
The numerical multiplier of a variable.
Example
In 7x2, the coefficient is 7.
Common Mistakes and Misconceptions — Algebraic Manipulation
The traps other students keep falling into on algebraic manipulation questions — taken from recent Pearson Edexcel IGCSE 4MA1 examiner reports and mark schemes — and how to avoid them.
✕Writing (a+b)2=a2+b2
4MA1/1H — examiner reports 2022-2024
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Why it happens
Distributing the square — but squaring isn't distributive over addition.
How to avoid it
(a+b)2=a2+2ab+b2. Three terms. Always include the cross-term 2ab.
✕Trying to FOIL three brackets at once
4MA1/2H Jan 2024 — examiner report Q6
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Why it happens
Looking for shortcuts.
How to avoid it
Do TWO brackets first → quadratic. Multiply that quadratic by the third bracket. Mark scheme awards method marks for the intermediate quadratic.
✕Sign errors when expanding −(a+b)
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Why it happens
Forgetting the minus distributes to BOTH terms.
How to avoid it
−(a+b)=−a−b. Both signs flip. Test: −(3+2)=−5, NOT −3+2=−1.
✕Combining x and x2 as like terms
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Why it happens
Both have the variable x.
How to avoid it
Like terms need same variable AND same power. x and x2 are unlike terms; cannot be combined.
Practice questions
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