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JAMB Mathematics 1997 Question 18

Question 18

Inequalities

Find the range of value of x which satisfies the inequality 12x2 < x + 1.

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

Answer: A (−1/4 < x < 1/3)

Explanation

12x² − x − 1 < 0 factorises as (4x + 1)(3x − 1) < 0, which holds between the roots: −1/4 < x < 1/3.