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JAMB Mathematics 2009 Question 16

Question 16

Inequalities

Determine the value of x for which (x2 − 1) > 0.

  1. A.x < −1 or x > 1
  2. B.−1 < x < 1
  3. C.x > 0
  4. D.x < −1
Show the answer and explanation

Answer: A (x < −1 or x > 1)

Explanation

x2 − 1 = (x − 1)(x + 1) is positive when both factors have the same sign, i.e. x < −1 or x > 1.