Find the Determinant [[3,1],[3,9]]

$[\begin{array}{c} 3 & 1 \\ 3 & 9 \end{array}]$

Step 1

The determinant of a $2 \times 2$ matrix can be found using the formula $| \begin{array}{c} a & b \\ c & d \end{array} | = a d - c b$ .

$3 \cdot 9 - 3 \cdot 1$

Step 2

Simplify the determinant.

Simplify each term.

Multiply $3$ by $9$ .

$27 - 3 \cdot 1$

Multiply $- 3$ by $1$ .

$27 - 3$

Subtract $3$ from $27$ .

$24$