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JAMB Mathematics 2014 Question 23

Question 23

Matrices and Determinants

If the determinant |−x 12 / −1 4| = −12, find x.
(rows: −x, 12 and −1, 4)

  1. A.6
  2. B.−6
  3. C.−2
  4. D.3
Show the answer and explanation

Answer: A (6)

Explanation

The determinant is (−x)(4) − (12)(−1) = −4x + 12. Setting −4x + 12 = −12 gives x = 6.