Linear Algebra Examples

$[\begin{array}{c} - 4 & 10 \\ 5 & 6 \end{array}]$

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

$- 4 \cdot 6 - 5 \cdot 10$

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 $- 4$ by $6$ .

$- 24 - 5 \cdot 10$

Step 2.2.1.2

Multiply $- 5$ by $10$ .

$- 24 - 50$

Step 2.2.2

Subtract $50$ from $- 24$ .

$- 74$

Step 3

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

Step 4

Substitute the known values into the formula for the inverse.

$\frac{1}{- 74} [\begin{array}{c} 6 & - 10 \\ - 5 & - 4 \end{array}]$

Step 5

Move the negative in front of the fraction.

$- \frac{1}{74} [\begin{array}{c} 6 & - 10 \\ - 5 & - 4 \end{array}]$

Step 6

Multiply $- \frac{1}{74}$ by each element of the matrix.

$[\begin{array}{c} - \frac{1}{74} \cdot 6 & - \frac{1}{74} \cdot - 10 \\ - \frac{1}{74} \cdot - 5 & - \frac{1}{74} \cdot - 4 \end{array}]$

Step 7

Simplify each element in the matrix.

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Step 7.1

Cancel the common factor of $2$ .

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Step 7.1.1

Move the leading negative in $- \frac{1}{74}$ into the numerator.

$[\begin{array}{c} \frac{- 1}{74} \cdot 6 & - \frac{1}{74} \cdot - 10 \\ - \frac{1}{74} \cdot - 5 & - \frac{1}{74} \cdot - 4 \end{array}]$

Step 7.1.2

Factor $2$ out of $74$ .

$[\begin{array}{c} \frac{- 1}{2 (37)} \cdot 6 & - \frac{1}{74} \cdot - 10 \\ - \frac{1}{74} \cdot - 5 & - \frac{1}{74} \cdot - 4 \end{array}]$

Step 7.1.3

Factor $2$ out of $6$ .

$[\begin{array}{c} \frac{- 1}{2 \cdot 37} \cdot (2 \cdot 3) & - \frac{1}{74} \cdot - 10 \\ - \frac{1}{74} \cdot - 5 & - \frac{1}{74} \cdot - 4 \end{array}]$

Step 7.1.4

Cancel the common factor.

$[\begin{array}{c} \frac{- 1}{2 \cdot 37} \cdot (2 \cdot 3) & - \frac{1}{74} \cdot - 10 \\ - \frac{1}{74} \cdot - 5 & - \frac{1}{74} \cdot - 4 \end{array}]$

Step 7.1.5

Rewrite the expression.

$[\begin{array}{c} \frac{- 1}{37} \cdot 3 & - \frac{1}{74} \cdot - 10 \\ - \frac{1}{74} \cdot - 5 & - \frac{1}{74} \cdot - 4 \end{array}]$

Step 7.2

Combine $\frac{- 1}{37}$ and $3$ .

$[\begin{array}{c} \frac{- 1 \cdot 3}{37} & - \frac{1}{74} \cdot - 10 \\ - \frac{1}{74} \cdot - 5 & - \frac{1}{74} \cdot - 4 \end{array}]$

Step 7.3

Multiply $- 1$ by $3$ .

$[\begin{array}{c} \frac{- 3}{37} & - \frac{1}{74} \cdot - 10 \\ - \frac{1}{74} \cdot - 5 & - \frac{1}{74} \cdot - 4 \end{array}]$

Step 7.4

Move the negative in front of the fraction.

$[\begin{array}{c} - \frac{3}{37} & - \frac{1}{74} \cdot - 10 \\ - \frac{1}{74} \cdot - 5 & - \frac{1}{74} \cdot - 4 \end{array}]$

Step 7.5

Cancel the common factor of $2$ .

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Step 7.5.1

Move the leading negative in $- \frac{1}{74}$ into the numerator.

$[\begin{array}{c} - \frac{3}{37} & \frac{- 1}{74} \cdot - 10 \\ - \frac{1}{74} \cdot - 5 & - \frac{1}{74} \cdot - 4 \end{array}]$

Step 7.5.2

Factor $2$ out of $74$ .

$[\begin{array}{c} - \frac{3}{37} & \frac{- 1}{2 (37)} \cdot - 10 \\ - \frac{1}{74} \cdot - 5 & - \frac{1}{74} \cdot - 4 \end{array}]$

Step 7.5.3

Factor $2$ out of $- 10$ .

$[\begin{array}{c} - \frac{3}{37} & \frac{- 1}{2 \cdot 37} \cdot (2 \cdot - 5) \\ - \frac{1}{74} \cdot - 5 & - \frac{1}{74} \cdot - 4 \end{array}]$

Step 7.5.4

Cancel the common factor.

$[\begin{array}{c} - \frac{3}{37} & \frac{- 1}{2 \cdot 37} \cdot (2 \cdot - 5) \\ - \frac{1}{74} \cdot - 5 & - \frac{1}{74} \cdot - 4 \end{array}]$

Step 7.5.5

Rewrite the expression.

$[\begin{array}{c} - \frac{3}{37} & \frac{- 1}{37} \cdot - 5 \\ - \frac{1}{74} \cdot - 5 & - \frac{1}{74} \cdot - 4 \end{array}]$

Step 7.6

Combine $\frac{- 1}{37}$ and $- 5$ .

$[\begin{array}{c} - \frac{3}{37} & \frac{- - 5}{37} \\ - \frac{1}{74} \cdot - 5 & - \frac{1}{74} \cdot - 4 \end{array}]$

Step 7.7

Multiply $- 1$ by $- 5$ .

$[\begin{array}{c} - \frac{3}{37} & \frac{5}{37} \\ - \frac{1}{74} \cdot - 5 & - \frac{1}{74} \cdot - 4 \end{array}]$

Step 7.8

Multiply $- \frac{1}{74} \cdot - 5$ .

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Step 7.8.1

Multiply $- 5$ by $- 1$ .

$[\begin{array}{c} - \frac{3}{37} & \frac{5}{37} \\ 5 (\frac{1}{74}) & - \frac{1}{74} \cdot - 4 \end{array}]$

Step 7.8.2

Combine $5$ and $\frac{1}{74}$ .

$[\begin{array}{c} - \frac{3}{37} & \frac{5}{37} \\ \frac{5}{74} & - \frac{1}{74} \cdot - 4 \end{array}]$

Step 7.9

Cancel the common factor of $2$ .

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Step 7.9.1

Move the leading negative in $- \frac{1}{74}$ into the numerator.

$[\begin{array}{c} - \frac{3}{37} & \frac{5}{37} \\ \frac{5}{74} & \frac{- 1}{74} \cdot - 4 \end{array}]$

Step 7.9.2

Factor $2$ out of $74$ .

$[\begin{array}{c} - \frac{3}{37} & \frac{5}{37} \\ \frac{5}{74} & \frac{- 1}{2 (37)} \cdot - 4 \end{array}]$

Step 7.9.3

Factor $2$ out of $- 4$ .

$[\begin{array}{c} - \frac{3}{37} & \frac{5}{37} \\ \frac{5}{74} & \frac{- 1}{2 \cdot 37} \cdot (2 \cdot - 2) \end{array}]$

Step 7.9.4

Cancel the common factor.

$[\begin{array}{c} - \frac{3}{37} & \frac{5}{37} \\ \frac{5}{74} & \frac{- 1}{2 \cdot 37} \cdot (2 \cdot - 2) \end{array}]$

Step 7.9.5

Rewrite the expression.

$[\begin{array}{c} - \frac{3}{37} & \frac{5}{37} \\ \frac{5}{74} & \frac{- 1}{37} \cdot - 2 \end{array}]$

Step 7.10

Combine $\frac{- 1}{37}$ and $- 2$ .

$[\begin{array}{c} - \frac{3}{37} & \frac{5}{37} \\ \frac{5}{74} & \frac{- - 2}{37} \end{array}]$

Step 7.11

Multiply $- 1$ by $- 2$ .

$[\begin{array}{c} - \frac{3}{37} & \frac{5}{37} \\ \frac{5}{74} & \frac{2}{37} \end{array}]$