NECO 2024 · Paper 1 · Q16

Matrices & determinants

Find the values of $x$ , $y$ and $z$ respectively for which $\begin{pmatrix} x & 2y \\ z & 9 \end{pmatrix} = \begin{pmatrix} 4 & 12 \\ 3 & 9 \end{pmatrix}$ .

Worked solution (try it first)

Equal matrices have equal entries in matching positions.
Top-left: $x = 4$ .
Top-right: $2y = 12$ , so $y = 6$ .
Bottom-left: $z = 3$ .
So $(x, y, z) = (4, 6, 3)$ , option B.

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