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WAEC Further Mathematics 2018 Question 15

Question 15

Matrices and Determinants

If |k k / 4 k| + |2 3 / −1 k| = 6, find the value of the constant k, where k > 0. (Determinants written row by row; / separates the rows.)

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

Answer: C (3)

Explanation

(k² − 4k) + (2k + 3) = 6 gives k² − 2k − 3 = 0, (k − 3)(k + 1) = 0, so k = 3 (k > 0).