Finite Math Examples

$4 A = [\begin{array}{c} 5 & 9 \\ 9 & 9 \end{array}]$

Step 1

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

$5 \cdot 9 - 9 \cdot 9$

Step 2

Simplify the determinant.

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Step 2.1

Simplify each term.

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Step 2.1.1

Multiply $5$ by $9$ .

$45 - 9 \cdot 9$

Step 2.1.2

Multiply $- 9$ by $9$ .

$45 - 81$

Step 2.2

Subtract $81$ from $45$ .

$- 36$