What Is a Matrix?

Matrix A = $\left(\begin{array}{cc}3& 5\\ -1& 4\end{array}\right)$. Find its order, and the element in row $1$, column $2$.

• 1Count the rows: $2$. Count the columns: $2$
• 2Order = $2\times 2$ (rows × columns)
• 3Row $1$, column $2$ is the top-right entry: $5$

Answer: Order = $2\times 2$, element = $5$

Find the order of $\left(\begin{array}{ccc}2& 0& 7\\ 1& 4& 9\end{array}\right)$.

• 1Rows: $2$. Columns: $3$
• 2Order = rows × columns

Answer: $2\times 3$. You will also meet $3\times 3$ matrices when computing larger determinants.