Find the Inverse [[2,5],[1,2]]

$[\begin{array}{c} 2 & 5 \\ 1 & 2 \end{array}]$

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 $| \begin{array}{c} a & b \\ c & d \end{array} | = a d - c b$ .

$2 \cdot 2 - 1 \cdot 5$

Simplify the determinant.

Simplify each term.

Multiply $2$ by $2$ .

$4 - 1 \cdot 5$

Multiply $- 1$ by $5$ .

$4 - 5$

Subtract $5$ from $4$ .

$- 1$

Step 3

Substitute the known values into the formula for the inverse.

$\frac{1}{- 1} [\begin{array}{c} 2 & - 5 \\ - 1 & 2 \end{array}]$

Step 4

Divide $1$ by $- 1$ .

$- [\begin{array}{c} 2 & - 5 \\ - 1 & 2 \end{array}]$

Step 5

Multiply $- 1$ by each element of the matrix.

$[\begin{array}{c} - 1 \cdot 2 & - - 5 \\ - - 1 & - 1 \cdot 2 \end{array}]$

Step 6

Simplify each element in the matrix.

Multiply $- 1$ by $2$ .

$[\begin{array}{c} - 2 & - - 5 \\ - - 1 & - 1 \cdot 2 \end{array}]$

Multiply $- 1$ by $- 5$ .

$[\begin{array}{c} - 2 & 5 \\ - - 1 & - 1 \cdot 2 \end{array}]$

Multiply $- 1$ by $- 1$ .

$[\begin{array}{c} - 2 & 5 \\ 1 & - 1 \cdot 2 \end{array}]$

Multiply $- 1$ by $2$ .

$[\begin{array}{c} - 2 & 5 \\ 1 & - 2 \end{array}]$

Find the Inverse [[2,5],[1,2]]

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