Find the Inverse [[2,-7],[7,-24]]

$[\begin{array}{c} 2 & - 7 \\ 7 & - 24 \end{array}]$

Step 1

The inverse of a $2 \times 2$ matrix can be found using the formula $\frac{1}{a d - b c} [\begin{array}{c} d & - b \\ - c & a \end{array}]$ where $a d - b c$ is the determinant.

Step 2

Find the determinant.

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

$2 \cdot - 24 - 7 \cdot - 7$

Simplify the determinant.

Simplify each term.

Multiply $2$ by $- 24$ .

$- 48 - 7 \cdot - 7$

Multiply $- 7$ by $- 7$ .

$- 48 + 49$

Add $- 48$ and $49$ .

$1$

Step 3

Substitute the known values into the formula for the inverse.

$\frac{1}{1} [\begin{array}{c} - 24 & 7 \\ - 7 & 2 \end{array}]$

Step 4

Divide $1$ by $1$ .

$1 [\begin{array}{c} - 24 & 7 \\ - 7 & 2 \end{array}]$

Step 5

Multiply $1$ by each element of the matrix.

$[\begin{array}{c} 1 \cdot - 24 & 1 \cdot 7 \\ 1 \cdot - 7 & 1 \cdot 2 \end{array}]$

Step 6

Simplify each element in the matrix.

Multiply $- 24$ by $1$ .

$[\begin{array}{c} - 24 & 1 \cdot 7 \\ 1 \cdot - 7 & 1 \cdot 2 \end{array}]$

Multiply $7$ by $1$ .

$[\begin{array}{c} - 24 & 7 \\ 1 \cdot - 7 & 1 \cdot 2 \end{array}]$

Multiply $- 7$ by $1$ .

$[\begin{array}{c} - 24 & 7 \\ - 7 & 1 \cdot 2 \end{array}]$

Multiply $2$ by $1$ .

$[\begin{array}{c} - 24 & 7 \\ - 7 & 2 \end{array}]$

Find the Inverse [[2,-7],[7,-24]]

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