Linear Algebra Examples

$[\begin{array}{c} 2 & 4 \\ 6 & 8 \end{array}]$

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.

Tap for more steps...

Step 2.1

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

$2 \cdot 8 - 6 \cdot 4$

Step 2.2

Simplify the determinant.

Tap for more steps...

Step 2.2.1

Simplify each term.

Tap for more steps...

Step 2.2.1.1

Multiply $2$ by $8$ .

$16 - 6 \cdot 4$

Step 2.2.1.2

Multiply $- 6$ by $4$ .

$16 - 24$

Step 2.2.2

Subtract $24$ from $16$ .

$- 8$

Step 3

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

Step 4

Substitute the known values into the formula for the inverse.

$\frac{1}{- 8} [\begin{array}{c} 8 & - 4 \\ - 6 & 2 \end{array}]$

Step 5

Move the negative in front of the fraction.

$- \frac{1}{8} [\begin{array}{c} 8 & - 4 \\ - 6 & 2 \end{array}]$

Step 6

Multiply $- \frac{1}{8}$ by each element of the matrix.

$[\begin{array}{c} - \frac{1}{8} \cdot 8 & - \frac{1}{8} \cdot - 4 \\ - \frac{1}{8} \cdot - 6 & - \frac{1}{8} \cdot 2 \end{array}]$

Step 7

Simplify each element in the matrix.

Tap for more steps...

Step 7.1

Cancel the common factor of $8$ .

Tap for more steps...

Step 7.1.1

Move the leading negative in $- \frac{1}{8}$ into the numerator.

$[\begin{array}{c} \frac{- 1}{8} \cdot 8 & - \frac{1}{8} \cdot - 4 \\ - \frac{1}{8} \cdot - 6 & - \frac{1}{8} \cdot 2 \end{array}]$

Step 7.1.2

Cancel the common factor.

$[\begin{array}{c} \frac{- 1}{8} \cdot 8 & - \frac{1}{8} \cdot - 4 \\ - \frac{1}{8} \cdot - 6 & - \frac{1}{8} \cdot 2 \end{array}]$

Step 7.1.3

Rewrite the expression.

$[\begin{array}{c} - 1 & - \frac{1}{8} \cdot - 4 \\ - \frac{1}{8} \cdot - 6 & - \frac{1}{8} \cdot 2 \end{array}]$

Step 7.2

Cancel the common factor of $4$ .

Tap for more steps...

Step 7.2.1

Move the leading negative in $- \frac{1}{8}$ into the numerator.

$[\begin{array}{c} - 1 & \frac{- 1}{8} \cdot - 4 \\ - \frac{1}{8} \cdot - 6 & - \frac{1}{8} \cdot 2 \end{array}]$

Step 7.2.2

Factor $4$ out of $8$ .

$[\begin{array}{c} - 1 & \frac{- 1}{4 (2)} \cdot - 4 \\ - \frac{1}{8} \cdot - 6 & - \frac{1}{8} \cdot 2 \end{array}]$

Step 7.2.3

Factor $4$ out of $- 4$ .

$[\begin{array}{c} - 1 & \frac{- 1}{4 \cdot 2} \cdot (4 \cdot - 1) \\ - \frac{1}{8} \cdot - 6 & - \frac{1}{8} \cdot 2 \end{array}]$

Step 7.2.4

Cancel the common factor.

$[\begin{array}{c} - 1 & \frac{- 1}{4 \cdot 2} \cdot (4 \cdot - 1) \\ - \frac{1}{8} \cdot - 6 & - \frac{1}{8} \cdot 2 \end{array}]$

Step 7.2.5

Rewrite the expression.

$[\begin{array}{c} - 1 & \frac{- 1}{2} \cdot - 1 \\ - \frac{1}{8} \cdot - 6 & - \frac{1}{8} \cdot 2 \end{array}]$

Step 7.3

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

$[\begin{array}{c} - 1 & \frac{- - 1}{2} \\ - \frac{1}{8} \cdot - 6 & - \frac{1}{8} \cdot 2 \end{array}]$

Step 7.4

Multiply $- 1$ by $- 1$ .

$[\begin{array}{c} - 1 & \frac{1}{2} \\ - \frac{1}{8} \cdot - 6 & - \frac{1}{8} \cdot 2 \end{array}]$

Step 7.5

Cancel the common factor of $2$ .

Tap for more steps...

Step 7.5.1

Move the leading negative in $- \frac{1}{8}$ into the numerator.

$[\begin{array}{c} - 1 & \frac{1}{2} \\ \frac{- 1}{8} \cdot - 6 & - \frac{1}{8} \cdot 2 \end{array}]$

Step 7.5.2

Factor $2$ out of $8$ .

$[\begin{array}{c} - 1 & \frac{1}{2} \\ \frac{- 1}{2 (4)} \cdot - 6 & - \frac{1}{8} \cdot 2 \end{array}]$

Step 7.5.3

Factor $2$ out of $- 6$ .

$[\begin{array}{c} - 1 & \frac{1}{2} \\ \frac{- 1}{2 \cdot 4} \cdot (2 \cdot - 3) & - \frac{1}{8} \cdot 2 \end{array}]$

Step 7.5.4

Cancel the common factor.

$[\begin{array}{c} - 1 & \frac{1}{2} \\ \frac{- 1}{2 \cdot 4} \cdot (2 \cdot - 3) & - \frac{1}{8} \cdot 2 \end{array}]$

Step 7.5.5

Rewrite the expression.

$[\begin{array}{c} - 1 & \frac{1}{2} \\ \frac{- 1}{4} \cdot - 3 & - \frac{1}{8} \cdot 2 \end{array}]$

Step 7.6

Combine $\frac{- 1}{4}$ and $- 3$ .

$[\begin{array}{c} - 1 & \frac{1}{2} \\ \frac{- - 3}{4} & - \frac{1}{8} \cdot 2 \end{array}]$

Step 7.7

Multiply $- 1$ by $- 3$ .

$[\begin{array}{c} - 1 & \frac{1}{2} \\ \frac{3}{4} & - \frac{1}{8} \cdot 2 \end{array}]$

Step 7.8

Cancel the common factor of $2$ .

Tap for more steps...

Step 7.8.1

Move the leading negative in $- \frac{1}{8}$ into the numerator.

$[\begin{array}{c} - 1 & \frac{1}{2} \\ \frac{3}{4} & \frac{- 1}{8} \cdot 2 \end{array}]$

Step 7.8.2

Factor $2$ out of $8$ .

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

Step 7.8.3

Cancel the common factor.

$[\begin{array}{c} - 1 & \frac{1}{2} \\ \frac{3}{4} & \frac{- 1}{2 \cdot 4} \cdot 2 \end{array}]$

Step 7.8.4

Rewrite the expression.

$[\begin{array}{c} - 1 & \frac{1}{2} \\ \frac{3}{4} & \frac{- 1}{4} \end{array}]$

Step 7.9

Move the negative in front of the fraction.

$[\begin{array}{c} - 1 & \frac{1}{2} \\ \frac{3}{4} & - \frac{1}{4} \end{array}]$