Introduction to Functions in MYP Year 5 Maths
Learn functions in MYP Maths Year 5: mapping diagrams, function notation f(x), domain and range, and the vertical line test with clear explanations and exam tips.
What Is a Function?
A function is a relationship that assigns exactly one output to every input. This sounds simple, but understanding it precisely is the foundation for everything else in Unit 3. In MYP Year 5, you are expected to move beyond a basic intuition and work with function notation and mapping diagrams fluently.
Key Concepts Covered
Mapping Diagrams
Mapping diagrams show how each element in the domain maps to exactly one element in the range. If any input maps to two outputs, the relationship is not a function. Practise drawing and interpreting these — they appear in Criterion A questions that test definitional knowledge.
Function Notation
You need to be comfortable with notation such as f(x) = 2x + 3. This means: apply the rule to the input x to get the output. Common tasks include evaluating f(3), solving f(x) = 11, or substituting an expression like f(x + 1).
Domain and Range
The domain is the set of all valid inputs. The range is the set of all possible outputs. At Standard level you will typically work with domains described in words or simple inequalities rather than formal interval notation.
The Vertical Line Test
A graph represents a function if and only if every vertical line crosses it at most once. This is a quick visual check you should be able to apply to any graph shown in an exam question.
Common Mistakes
- Confusing domain and range — domain is always the input (x), range is the output (y).
- Writing f(x) as if it means f multiplied by x.
- Missing cases where a diagram fails the function definition because one input has two arrows.
How to Practise
Work through mapping diagram exercises first, then move to evaluating function notation with substitution. Graph unfamiliar relations and apply the vertical line test. Write out the domain and range explicitly for every function you graph — this habit will help you in later topics.