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JAMB Mathematics 1999 Question 38

Question 38

Differentiation

Find the value of x for which the function y = x3 − x has a minimum value.

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

Answer: C (√3/3)

Explanation

dy/dx = 3x² − 1 = 0 gives x = ±1/√3. d²y/dx² = 6x is positive at x = 1/√3 = √3/3, so that is the minimum.