## Precalculus (6th Edition) Blitzer

Consider, $A-C=\left[ \begin{array}{*{35}{l}} 4 & 0 \\ -3 & 5 \\ 0 & 1 \\ \end{array} \right]-\left[ \begin{matrix} 1 & -1 \\ -1 & 1 \\ \end{matrix} \right]$ This subtraction cannot be defined because the matrix is of the size $2\times 3$ and matrix $C$ is of the size $2\times 2$. For subtraction, the size of both matrices must be the same. Here, the size of the matrix $A$ is different from the size of the matrix $C$. Therefore, the operation of subtraction is not defined.