Find the Determinant [[4,-1],[20,-5]]

$[\begin{array}{c} 4 & - 1 \\ 20 & - 5 \end{array}]$

Step 1

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

$4 \cdot - 5 - 20 \cdot - 1$

Step 2

Simplify the determinant.

Simplify each term.

Multiply $4$ by $- 5$ .

$- 20 - 20 \cdot - 1$

Multiply $- 20$ by $- 1$ .

$- 20 + 20$

Add $- 20$ and $20$ .

$0$