Exercise · ZW-TRANSPOSE-MATRIX-006 · ★★☆ Intermediate
With \(A=\begin{pmatrix}1 & 2 \\ 0 & 1\end{pmatrix}\) and \(B=\begin{pmatrix}3 & 0 \\ 1 & 2\end{pmatrix}\), compute \((AB)^T\).
Choose one option.
A \(\begin{pmatrix}3 & 1 \\ 6 & 4\end{pmatrix}\) B \(\begin{pmatrix}5 & 4 \\ 1 & 2\end{pmatrix}\) C \(\begin{pmatrix}5 & 1 \\ 4 & 2\end{pmatrix}\) D \(\begin{pmatrix}3 & 1 \\ 4 & 5\end{pmatrix}\)
Show answer C. \(\begin{pmatrix}5 & 1 \\ 4 & 2\end{pmatrix}\)
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Explanation First \(AB=\begin{pmatrix}5 & 4\\ 1 & 2\end{pmatrix}\), then transpose : \(\begin{pmatrix}5 & 1\\ 4 & 2\end{pmatrix}\). It equals \(B^TA^T\); \(A^TB^T\) gives a different result because order matters.
The transpose \(A^T\) of a matrix \(A\) is the one obtained by exchanging its rows and columns.
\[(A^T)_{ij}=a_{ji}\]
More practice problems: transpose matrix