GCSE Maths (Edexcel)

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Functions as Algebraic Expressions

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Algebra Notation, Vocabulary and Manipulation

Functions as Algebraic Expressions

3:22 Functions
Spec A7
Previous Function Notation Next Inverse Functions
  • The output of a function can be equal to an expression in terms of an algebraic variable representing the input.
  • The function f(x) = 2x means that the function takes an input x and returns two times the input.
  • To find the output of a function for a certain value, substitute that value into the function.
  • Example: f(x) = 2x - 1, find f(-2). Substitute -2 into the function and simplify to get f(-2) = -5.
  • In a mapping diagram, the function multiplies the input by 2 and subtracts 1.
  • Example: 0 -> -1, 1 -> 1, 2 -> 3, 3 -> 5.
  • The rule for the function f is to multiply the input by 2 and subtract 1.
  • The function f(x) = 2x - 1 expresses this rule for any input x.

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