WAEC Mathematics 2025 Theory — Question 13

Question 13 of 19 from the West African Examinations Council (WAEC) Mathematics 2025 Theory paper, with the correct answer and a full explanation.

11(a). Given that P = [[2, 4], [−9, 1]] and Q = [[1, −1], [3, −2]], find PQ + 2Q.

Model answer

PQ = [[2,4],[−9,1]] × [[1,−1],[3,−2]] = [[2+12, −2−8],[−9+3, 9−2]] = [[14,−10],[−6,7]] 2Q = [[2,−2],[6,−4]] PQ + 2Q = [[16,−12],[0,3]]

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