Finite Math Examples

$[\begin{array}{c} 2 & - 7 \\ - 1 & 4 \end{array}]$

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.

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Step 2.1

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

$2 \cdot 4 - - - 7$

Step 2.2

Simplify the determinant.

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Step 2.2.1

Simplify each term.

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Step 2.2.1.1

Multiply $2$ by $4$ .

$8 - - - 7$

Step 2.2.1.2

Multiply $- - - 7$ .

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Step 2.2.1.2.1

Multiply $- 1$ by $- 7$ .

$8 - 1 \cdot 7$

Step 2.2.1.2.2

Multiply $- 1$ by $7$ .

$8 - 7$

Step 2.2.2

Subtract $7$ from $8$ .

$1$

Step 3

Since the determinant is non-zero, the inverse exists.

Step 4

Substitute the known values into the formula for the inverse.

$\frac{1}{1} [\begin{array}{c} 4 & 7 \\ 1 & 2 \end{array}]$

Step 5

Divide $1$ by $1$ .

$1 [\begin{array}{c} 4 & 7 \\ 1 & 2 \end{array}]$

Step 6

Multiply $1$ by each element of the matrix.

$[\begin{array}{c} 1 \cdot 4 & 1 \cdot 7 \\ 1 \cdot 1 & 1 \cdot 2 \end{array}]$

Step 7

Simplify each element in the matrix.

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Step 7.1

Multiply $4$ by $1$ .

$[\begin{array}{c} 4 & 1 \cdot 7 \\ 1 \cdot 1 & 1 \cdot 2 \end{array}]$

Step 7.2

Multiply $7$ by $1$ .

$[\begin{array}{c} 4 & 7 \\ 1 \cdot 1 & 1 \cdot 2 \end{array}]$

Step 7.3

Multiply $1$ by $1$ .

$[\begin{array}{c} 4 & 7 \\ 1 & 1 \cdot 2 \end{array}]$

Step 7.4

Multiply $2$ by $1$ .

$[\begin{array}{c} 4 & 7 \\ 1 & 2 \end{array}]$