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JAMB Mathematics 2006 Question 12

Question 12

Differentiation

Find the value of x for which the function 3x3 − 9x2 is minimum.

  1. A.0
  2. B.2
  3. C.3
  4. D.5
Show the answer and explanation

Answer: B (2)

Explanation

f'(x) = 9x2 − 18x = 9x(x − 2) = 0 at x = 0 or 2. f''(2) = 54 − 18 > 0, so the minimum is at x = 2.