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Year 8 · Functions & Graphs

Tables of values and function rules

Function notation f(x) means "the rule applied to x". f(3) is the rule with 3 put in.

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How to do it

  1. Substitute the number for every x.
  2. Composite f(g(x)): work out g first, then put the result into f.
  3. Inverse: swap x and y, then make y the subject.

Worked example

f(x) = 5x + 0. Find f(3).
Replace x with 3: 5 × (3) + 0 = 15.
Answer: 15

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Inside brackets first for composite functions.

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