ECZ 2018 · GCE Paper 1 — Matrices

Given that C = [5 −1; 2 1] (a 2×2 matrix with rows separated by semicolons) and D = [1; −2] (a column vector), express CD as a single matrix.

  • A. [3; 0]
  • B. [7; 0]
  • C. [7; 4]
  • D. [3; 4]

Verified working — step 1

Each row of C multiplies down the column D. Top: (5)(1) + (−1)(−2) = 5 + 2 = 7. Bottom: (2)(1) + (1)(−2) = 2 − 2 = 0. So CD = …

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Original examination question © Examinations Council of Zambia. Worked solution and commentary © G12 Titan — not to be reproduced without permission.

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