Study Notes
Expressions and formulae involve substituting values into expressions and rearranging equations to make a variable the subject.
- Substitution — replacing a variable with a given value and calculating the result. Example: Find the value of 3m – 5 when m = 6. 3m – 5 = 3 x 6 – 5 = 18 – 5 = 13.
- Making a variable the subject — rearranging an equation so that the variable is isolated on one side. Example: In the formula A = bh, A is the subject.
Exam Tips
Key Definitions to Remember
- Substitution: Replacing a variable with a given value.
- Subject of a formula: The variable isolated on one side of the equation.
Common Confusions
- Forgetting to follow the order of operations when substituting values.
- Not isolating the variable completely when making it the subject.
Typical Exam Questions
- What is the value of 3x + 4y when x = 10 and y = 2? 38
- How do you make x the subject in the equation 2x + 3 = 7? x = 2
- Find the value of when e = 4. Substitute and calculate
What Examiners Usually Test
- Ability to correctly substitute values into expressions.
- Skill in rearranging equations to make a variable the subject.