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JAMB Mathematics 2009 Question 38

Question 38

Differentiation

What value of x will make the function x(4 − x) a maximum?

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

Answer: C (2)

Explanation

y = 4x − x2 gives dy/dx = 4 − 2x = 0 at x = 2, and the second derivative −2 is negative, so this is a maximum.