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WAEC Further Mathematics 2013 Question 32

Question 32

Matrices and Determinants

Given that P = (3 4 / 2 x), Q = (1 3 / −2 4), R = (−5 25 / −8 26) and PQ = R, find the value of x. (Matrices written row by row; / separates the rows.)

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

Answer: D (5)

Explanation

PQ = (−5 25 / 2 − 2x 6 + 4x). So 2 − 2x = −8 (and 6 + 4x = 26), giving x = 5.