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JAMB Mathematics 2008 Question 24

Question 24

Matrices and Determinants

If (−2 1; 2 3)(p q; r s) = (1 0; 0 1), what is the value of r? (Matrices written row by row.)

  1. A.−3/8
  2. B.3/8
  3. C.5/8
  4. D.1/4
Show the answer and explanation

Answer: D (1/4)

Explanation

(p q; r s) is the inverse of (−2 1; 2 3). The determinant is −6 − 2 = −8, so r = −2/(−8) = 1/4.