CIE 0580 Algebra: 7 Common Mistakes and How to Fix Them

Algebra questions in CIE 0580 are predictable — but small mistakes can cost full marks.
Use this checklist to fix the most common errors before your next exam.

1) Sign errors when expanding brackets

Fix: Write one line for each term, then combine like terms.
Tip: Double‑check negative signs by substituting a simple value (e.g., x = 1).

2) Factorising misses a common factor

Fix: Always take out the greatest common factor first.
Example: 6x^2 + 9x = 3x(2x + 3).

3) Solving linear equations too early

Fix: Simplify both sides before moving terms.
This reduces errors when you have fractions or brackets.

4) Mixing up “equation” and “expression”

Fix: Only solve when there is an equals sign.
Otherwise, you simplify or factorise.

5) Incorrect substitution into formulas

Fix: Replace variables with brackets before you calculate.
Example: y = 2x + 3 with x = -4 → y = 2(-4) + 3.

6) Cancelling terms incorrectly

Fix: You can cancel factors, not terms.
Example: x + 2 cannot cancel with x.

7) Ignoring domain restrictions

Fix: Check if the question asks for valid values or restrictions.

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