Language of Functions (AQA A Level Maths): Revision Note

Language of functions

What language is used with functions?

• The language of functions has many keywords associated with it that need to be understood 

What are mappings?

• A mapping takes an ‘input’ from one set of values to an ‘output’ in another

• Mappings can be

  • ‘many-to-one’ (many ‘input’ values go to one ‘output’ value)

  • ‘one-to-many’

  • ‘many-to-many’

  • ‘one-to-one’

What is the difference between a mapping and a function?

• A function is a mapping where every ‘input’ value maps to a single ‘output’

• Many-to-one and one-to-one mappings are functions

• Mappings which have many possible outputs are not functions

What is function notation?

• Functions are denoted by the notation f(x), g(x), etc

  • eg. f(x) = x² - 3x + 2

• Or the alternative notation

  • eg. f : x ↦ x² – 3x + 2

What sets of numbers do I need to know?

• Functions often involve domains and ranges for specific sets of numbers

• All numbers can be organised into different sets ℕ, ℤ, ℚ, ℝ

• So ℕ is a subset of ℤ etc

• ℤ^- would be the set of negative integers only

What is the domain of a function?

• The domain of a function is the set of values that are allowed to be the ‘input’

• A function is only fully defined once its domain has been stated

• Restrictions on a domain can turn many-to-one functions into one-to-one functions

What is the range of a function?

• The range of a function is the set of values of all possible ‘outputs’

  

• The type of values in the range depend on the domain