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WAEC Further Mathematics 2011 Question 12

Question 12

Differentiation

f(x) = (x2 + 3)2 is defined on the set of real numbers R. Find the gradient of f(x) at x = 1/2.

  1. A.4.0
  2. B.6.5
  3. C.5.0
  4. D.10.6
Show the answer and explanation

Answer: B (6.5)

Explanation

f'(x) = 2(x2 + 3) × 2x = 4x(x2 + 3). At x = ½: 2 × 3.25 = 6.5.