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WAEC Further Mathematics 2007 Question 5

Question 5

Functions

Two functions f and g are defined on the set R of real numbers by f : x → 2x − 1 and g : x → x2 + 1. Find the value of f−1 o g(3).

  1. A.12
  2. B.11
  3. C.11/2
  4. D.9/2
Show the answer and explanation

Answer: C (11/2)

Explanation

g(3) = 10. The inverse of f is f−1(x) = (x + 1)/2, so f−1(10) = 11/2.