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WAEC Further Mathematics 2011 Question 17

Question 17

Functions

The inverse of a function is given by f−1 : x → (x + 1)/4. Find f.

  1. A.f : x → 4x − 1
  2. B.f : x → 4x + 1
  3. C.f : x → 4x − ½
  4. D.f : x → x − ¼
Show the answer and explanation

Answer: A (f : x → 4x − 1)

Explanation

Let y = (x + 1)/4; then x = 4y − 1. So f is the inverse of f−1: f(x) = 4x − 1.