Find the Determinant [[-7,9],[1,1]]

$[\begin{array}{c} - 7 & 9 \\ 1 & 1 \end{array}]$

These are both valid notations for the determinant of a matrix.

$determinant [\begin{array}{c} - 7 & 9 \\ 1 & 1 \end{array}] = | \begin{array}{c} - 7 & 9 \\ 1 & 1 \end{array} |$

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

$(- 7) (1) - 1 \cdot 9$

Simplify the determinant.

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Simplify each term.

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Multiply $- 7$ by $1$ .

$- 7 - 1 \cdot 9$

Multiply $- 1$ by $9$ .

$- 7 - 9$

Subtract $9$ from $- 7$ .

$- 16$

Find the Determinant [[-7,9],[1,1]]

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