AlgebraExam Tips

Substitution: Common Mistakes to Avoid

Part of Simplifying Expressions · GCSE GCSE Mathematics revision

This exam tips covers Substitution: Common Mistakes to Avoid within Simplifying Expressions for GCSE Mathematics. Revise Simplifying Expressions in Algebra for GCSE Mathematics with 11 exam-style questions and 5 flashcards. Use this page as part of a wider topic revision path rather than treating it as an isolated fact. It is section 14 of 19 in this topic. Treat this as a marking guide for what examiners are looking for, not just a fact list.

Topic position

Section 14 of 19

Practice

11 questions

Recall

5 flashcards

Substitution: Common Mistakes to Avoid

✗ (−3)² = −9 ✓ (−3)² = (−3)×(−3) = 9 Negative × negative = positive!

✗ 2x² when x=3 gives 6² = 36 ✓ 2(3²) = 2(9) = 18 Square the x first, then multiply by 2

✗ Forgetting BIDMAS ✓ Do powers before multiplication x² + 3x: do x² first, then 3x, then add

✗ −3² = 9 ✓ −3² = −(3²) = −9 Without brackets, the minus stays separate

Keep building this topic

Read this section alongside the surrounding pages in Simplifying Expressions. That gives you the full topic sequence instead of a single isolated revision point.

Worked Example 6: Negative Values (Tricky!)Words to Algebra What Does "Simplify" Mean?What Are "Like Terms"?

Practice Questions for Simplifying Expressions

Which two terms are like terms?

A. 3x and 3y
B. 2x² and 5x
C. 4ab and 7ba
D. 6 and 6x

1 markfoundation

Explain why 3x + 2x² cannot be simplified to 5x³.

2 markshigher

Quick Recall Flashcards

Substitution

Replace each letter with its given value, then calculate

Like Terms

Terms with same letter and power: 2x and 5x are like terms

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Worked Example 6: Negative Values (Tricky!)

Words to Algebra