GCSE Maths (Edexcel)

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Advanced Composite Functions

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Algebra Notation, Vocabulary and Manipulation

Advanced Composite Functions

5:42 Inverse & Composite Functions
Spec A7
Previous Composite Functions Next x & y Axes
  • The value of a composite function can be found by substituting in known values
  • To find the value of fg evaluated with an input of 2, first find g(2) and then substitute it into f(x)
  • Example: f(x) = 1/2x - 4, g(x) = x^2 - 8. Find fg(2)
  • Substitute x=2 into g(x) to find g(2) = -4
  • Substitute g(2) into f(x) to find fg(2) = -6
  • Another example: f(x) = x - 1, g(x) = 2x. Find ff(g(1))
  • Substitute x=1 into g(x) to find g(1) = 2
  • Substitute g(1) into f(x) to find fg(1) = 1
  • Substitute fg(1) into f(x) to find ffg(1) = 0

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