Year 9 - Maths
Additive relationships
Expressions and formulae
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This pupil-friendly study guide includes a unit summary, clear notes, common mistakes, and quick questions with answers.
Unit Summary
This unit develops pupil understanding of formulae and how to rearrange them. Pupils will learn how to recognise and manipulate binomials and learn to recognise the difference of two squares.
Lesson Summary
You will learn to appreciate that an additive relationship between variables can be written in a number of different ways.
Key Notes
- When adding or subtracting, terms may only be combined if the order of each variable in each term is the same.
- The sum of the terms can be thought of as a term, despite being comprised of multiple terms.
- a + b = c also means that a = c − b
- a = c − b can also be written as a = c + (−b)
Vocabulary To Learn
- Equation: An equation is used to show two expressions that are equal to each other.
Common Mistakes To Avoid
- Rearranging equations means you can just swap where terms are.
3 Quick Questions (With Answers)
1. Solve this in steps: explain the method from this lesson and why each step matters.
When adding or subtracting, terms may only be combined if the order of each variable in each term is the same. The sum of the terms can be thought of as a term, despite being comprised of multiple terms.
2. Use this key word in a maths sentence and explain it clearly. 'Equation'
An equation is used to show two expressions that are equal to each other. Use this word when showing your method, then check your final answer is reasonable.
3. Spot and fix this common maths mistake.
Mistake: Rearranging equations means you can just swap where terms are. Correction: Remind pupils that subtraction and division are not commutative so swapping the order will matter.
More Lessons In This Unit
- Changing the subject to suit the context Study Guide
- Changing the subject with more complex formula Study Guide
- Changing the subject with simple formula Study Guide
- Checking and securing solving linear equations Study Guide
- Checking and securing understanding of the distributive law with algebraic terms Study Guide
- Difference of two squares Study Guide
- Evaluating expressions with and without changing the subject Study Guide
- More complex binomial products Study Guide
- Multiplicative relationships between terms Study Guide
- Problem solving with expressions and formulae Study Guide
- The product of two binomials Study Guide
Browse all guides in the Year 9 Maths guide library.