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Unilorin Post-UTME Mathematics 2023 (Model questions) Question 4

Question 4

Matrices and Determinants

If A = [−1 −1 −1; 3 1 −1; 1 2 1] (rows separated by semicolons), find |A|

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

Answer: C (−4)

Explanation

Expanding along the first row: −1(1×1 − (−1)×2) + 1(3×1 − (−1)×1) − 1(3×2 − 1×1) = −3 + 4 − 5 = −4.