Linear Algebra Examples

$[\begin{array}{c} - \frac{9}{7} & \frac{1}{7} & - \frac{3}{7} \\ \frac{40}{21} & - \frac{2}{7} & \frac{11}{21} \\ - \frac{47}{7} & \frac{6}{7} & - \frac{18}{7} \end{array}]$

Step 1

Choose the row or column with the most $0$ elements. If there are no $0$ elements choose any row or column. Multiply every element in row $1$ by its cofactor and add.

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Step 1.1

Consider the corresponding sign chart.

$| \begin{array}{c} + & - & + \\ - & + & - \\ + & - & + \end{array} |$

Step 1.2

The cofactor is the minor with the sign changed if the indices match a $-$ position on the sign chart.

Step 1.3

The minor for $a_{11}$ is the determinant with row $1$ and column $1$ deleted.

$| \begin{array}{c} - \frac{2}{7} & \frac{11}{21} \\ \frac{6}{7} & - \frac{18}{7} \end{array} |$

Step 1.4

Multiply element $a_{11}$ by its cofactor.

$- \frac{9}{7} | \begin{array}{c} - \frac{2}{7} & \frac{11}{21} \\ \frac{6}{7} & - \frac{18}{7} \end{array} |$

Step 1.5

The minor for $a_{12}$ is the determinant with row $1$ and column $2$ deleted.

$| \begin{array}{c} \frac{40}{21} & \frac{11}{21} \\ - \frac{47}{7} & - \frac{18}{7} \end{array} |$

Step 1.6

Multiply element $a_{12}$ by its cofactor.

$- \frac{1}{7} | \begin{array}{c} \frac{40}{21} & \frac{11}{21} \\ - \frac{47}{7} & - \frac{18}{7} \end{array} |$

Step 1.7

The minor for $a_{13}$ is the determinant with row $1$ and column $3$ deleted.

$| \begin{array}{c} \frac{40}{21} & - \frac{2}{7} \\ - \frac{47}{7} & \frac{6}{7} \end{array} |$

Step 1.8

Multiply element $a_{13}$ by its cofactor.

$- \frac{3}{7} | \begin{array}{c} \frac{40}{21} & - \frac{2}{7} \\ - \frac{47}{7} & \frac{6}{7} \end{array} |$

Step 1.9

Add the terms together.

$- \frac{9}{7} | \begin{array}{c} - \frac{2}{7} & \frac{11}{21} \\ \frac{6}{7} & - \frac{18}{7} \end{array} | - \frac{1}{7} | \begin{array}{c} \frac{40}{21} & \frac{11}{21} \\ - \frac{47}{7} & - \frac{18}{7} \end{array} | - \frac{3}{7} | \begin{array}{c} \frac{40}{21} & - \frac{2}{7} \\ - \frac{47}{7} & \frac{6}{7} \end{array} |$

Step 2

Evaluate $| \begin{array}{c} - \frac{2}{7} & \frac{11}{21} \\ \frac{6}{7} & - \frac{18}{7} \end{array} |$ .

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Step 2.1

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

$- \frac{9}{7} (- \frac{2}{7} (- \frac{18}{7}) - \frac{6}{7} \cdot \frac{11}{21}) - \frac{1}{7} | \begin{array}{c} \frac{40}{21} & \frac{11}{21} \\ - \frac{47}{7} & - \frac{18}{7} \end{array} | - \frac{3}{7} | \begin{array}{c} \frac{40}{21} & - \frac{2}{7} \\ - \frac{47}{7} & \frac{6}{7} \end{array} |$

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 $- \frac{2}{7} (- \frac{18}{7})$ .

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Step 2.2.1.1.1

Multiply $- 1$ by $- 1$ .

$- \frac{9}{7} (1 (\frac{2}{7}) \frac{18}{7} - \frac{6}{7} \cdot \frac{11}{21}) - \frac{1}{7} | \begin{array}{c} \frac{40}{21} & \frac{11}{21} \\ - \frac{47}{7} & - \frac{18}{7} \end{array} | - \frac{3}{7} | \begin{array}{c} \frac{40}{21} & - \frac{2}{7} \\ - \frac{47}{7} & \frac{6}{7} \end{array} |$

Step 2.2.1.1.2

Multiply $\frac{2}{7}$ by $1$ .

$- \frac{9}{7} (\frac{2}{7} \cdot \frac{18}{7} - \frac{6}{7} \cdot \frac{11}{21}) - \frac{1}{7} | \begin{array}{c} \frac{40}{21} & \frac{11}{21} \\ - \frac{47}{7} & - \frac{18}{7} \end{array} | - \frac{3}{7} | \begin{array}{c} \frac{40}{21} & - \frac{2}{7} \\ - \frac{47}{7} & \frac{6}{7} \end{array} |$

Step 2.2.1.1.3

Multiply $\frac{2}{7}$ by $\frac{18}{7}$ .

$- \frac{9}{7} (\frac{2 \cdot 18}{7 \cdot 7} - \frac{6}{7} \cdot \frac{11}{21}) - \frac{1}{7} | \begin{array}{c} \frac{40}{21} & \frac{11}{21} \\ - \frac{47}{7} & - \frac{18}{7} \end{array} | - \frac{3}{7} | \begin{array}{c} \frac{40}{21} & - \frac{2}{7} \\ - \frac{47}{7} & \frac{6}{7} \end{array} |$

Step 2.2.1.1.4

Multiply $2$ by $18$ .

$- \frac{9}{7} (\frac{36}{7 \cdot 7} - \frac{6}{7} \cdot \frac{11}{21}) - \frac{1}{7} | \begin{array}{c} \frac{40}{21} & \frac{11}{21} \\ - \frac{47}{7} & - \frac{18}{7} \end{array} | - \frac{3}{7} | \begin{array}{c} \frac{40}{21} & - \frac{2}{7} \\ - \frac{47}{7} & \frac{6}{7} \end{array} |$

Step 2.2.1.1.5

Multiply $7$ by $7$ .

$- \frac{9}{7} (\frac{36}{49} - \frac{6}{7} \cdot \frac{11}{21}) - \frac{1}{7} | \begin{array}{c} \frac{40}{21} & \frac{11}{21} \\ - \frac{47}{7} & - \frac{18}{7} \end{array} | - \frac{3}{7} | \begin{array}{c} \frac{40}{21} & - \frac{2}{7} \\ - \frac{47}{7} & \frac{6}{7} \end{array} |$

Step 2.2.1.2

Cancel the common factor of $3$ .

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Step 2.2.1.2.1

Move the leading negative in $- \frac{6}{7}$ into the numerator.

$- \frac{9}{7} (\frac{36}{49} + \frac{- 6}{7} \cdot \frac{11}{21}) - \frac{1}{7} | \begin{array}{c} \frac{40}{21} & \frac{11}{21} \\ - \frac{47}{7} & - \frac{18}{7} \end{array} | - \frac{3}{7} | \begin{array}{c} \frac{40}{21} & - \frac{2}{7} \\ - \frac{47}{7} & \frac{6}{7} \end{array} |$

Step 2.2.1.2.2

Factor $3$ out of $- 6$ .

$- \frac{9}{7} (\frac{36}{49} + \frac{3 (- 2)}{7} \cdot \frac{11}{21}) - \frac{1}{7} | \begin{array}{c} \frac{40}{21} & \frac{11}{21} \\ - \frac{47}{7} & - \frac{18}{7} \end{array} | - \frac{3}{7} | \begin{array}{c} \frac{40}{21} & - \frac{2}{7} \\ - \frac{47}{7} & \frac{6}{7} \end{array} |$

Step 2.2.1.2.3

Factor $3$ out of $21$ .

$- \frac{9}{7} (\frac{36}{49} + \frac{3 \cdot - 2}{7} \cdot \frac{11}{3 \cdot 7}) - \frac{1}{7} | \begin{array}{c} \frac{40}{21} & \frac{11}{21} \\ - \frac{47}{7} & - \frac{18}{7} \end{array} | - \frac{3}{7} | \begin{array}{c} \frac{40}{21} & - \frac{2}{7} \\ - \frac{47}{7} & \frac{6}{7} \end{array} |$

Step 2.2.1.2.4

Cancel the common factor.

Step 2.2.1.2.5

Rewrite the expression.

$- \frac{9}{7} (\frac{36}{49} + \frac{- 2}{7} \cdot \frac{11}{7}) - \frac{1}{7} | \begin{array}{c} \frac{40}{21} & \frac{11}{21} \\ - \frac{47}{7} & - \frac{18}{7} \end{array} | - \frac{3}{7} | \begin{array}{c} \frac{40}{21} & - \frac{2}{7} \\ - \frac{47}{7} & \frac{6}{7} \end{array} |$

Step 2.2.1.3

Multiply $\frac{- 2}{7}$ by $\frac{11}{7}$ .

$- \frac{9}{7} (\frac{36}{49} + \frac{- 2 \cdot 11}{7 \cdot 7}) - \frac{1}{7} | \begin{array}{c} \frac{40}{21} & \frac{11}{21} \\ - \frac{47}{7} & - \frac{18}{7} \end{array} | - \frac{3}{7} | \begin{array}{c} \frac{40}{21} & - \frac{2}{7} \\ - \frac{47}{7} & \frac{6}{7} \end{array} |$

Step 2.2.1.4

Multiply $- 2$ by $11$ .

$- \frac{9}{7} (\frac{36}{49} + \frac{- 22}{7 \cdot 7}) - \frac{1}{7} | \begin{array}{c} \frac{40}{21} & \frac{11}{21} \\ - \frac{47}{7} & - \frac{18}{7} \end{array} | - \frac{3}{7} | \begin{array}{c} \frac{40}{21} & - \frac{2}{7} \\ - \frac{47}{7} & \frac{6}{7} \end{array} |$

Step 2.2.1.5

Multiply $7$ by $7$ .

$- \frac{9}{7} (\frac{36}{49} + \frac{- 22}{49}) - \frac{1}{7} | \begin{array}{c} \frac{40}{21} & \frac{11}{21} \\ - \frac{47}{7} & - \frac{18}{7} \end{array} | - \frac{3}{7} | \begin{array}{c} \frac{40}{21} & - \frac{2}{7} \\ - \frac{47}{7} & \frac{6}{7} \end{array} |$

Step 2.2.1.6

Move the negative in front of the fraction.

$- \frac{9}{7} (\frac{36}{49} - \frac{22}{49}) - \frac{1}{7} | \begin{array}{c} \frac{40}{21} & \frac{11}{21} \\ - \frac{47}{7} & - \frac{18}{7} \end{array} | - \frac{3}{7} | \begin{array}{c} \frac{40}{21} & - \frac{2}{7} \\ - \frac{47}{7} & \frac{6}{7} \end{array} |$

Step 2.2.2

Combine the numerators over the common denominator.

$- \frac{9}{7} \cdot \frac{36 - 22}{49} - \frac{1}{7} | \begin{array}{c} \frac{40}{21} & \frac{11}{21} \\ - \frac{47}{7} & - \frac{18}{7} \end{array} | - \frac{3}{7} | \begin{array}{c} \frac{40}{21} & - \frac{2}{7} \\ - \frac{47}{7} & \frac{6}{7} \end{array} |$

Step 2.2.3

Subtract $22$ from $36$ .

$- \frac{9}{7} \cdot \frac{14}{49} - \frac{1}{7} | \begin{array}{c} \frac{40}{21} & \frac{11}{21} \\ - \frac{47}{7} & - \frac{18}{7} \end{array} | - \frac{3}{7} | \begin{array}{c} \frac{40}{21} & - \frac{2}{7} \\ - \frac{47}{7} & \frac{6}{7} \end{array} |$

Step 2.2.4

Cancel the common factor of $14$ and $49$ .

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Step 2.2.4.1

Factor $7$ out of $14$ .

$- \frac{9}{7} \cdot \frac{7 (2)}{49} - \frac{1}{7} | \begin{array}{c} \frac{40}{21} & \frac{11}{21} \\ - \frac{47}{7} & - \frac{18}{7} \end{array} | - \frac{3}{7} | \begin{array}{c} \frac{40}{21} & - \frac{2}{7} \\ - \frac{47}{7} & \frac{6}{7} \end{array} |$

Step 2.2.4.2

Cancel the common factors.

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Step 2.2.4.2.1

Factor $7$ out of $49$ .

$- \frac{9}{7} \cdot \frac{7 \cdot 2}{7 \cdot 7} - \frac{1}{7} | \begin{array}{c} \frac{40}{21} & \frac{11}{21} \\ - \frac{47}{7} & - \frac{18}{7} \end{array} | - \frac{3}{7} | \begin{array}{c} \frac{40}{21} & - \frac{2}{7} \\ - \frac{47}{7} & \frac{6}{7} \end{array} |$

Step 2.2.4.2.2

Cancel the common factor.

Step 2.2.4.2.3

Rewrite the expression.

$- \frac{9}{7} \cdot \frac{2}{7} - \frac{1}{7} | \begin{array}{c} \frac{40}{21} & \frac{11}{21} \\ - \frac{47}{7} & - \frac{18}{7} \end{array} | - \frac{3}{7} | \begin{array}{c} \frac{40}{21} & - \frac{2}{7} \\ - \frac{47}{7} & \frac{6}{7} \end{array} |$

Step 3

Evaluate $| \begin{array}{c} \frac{40}{21} & \frac{11}{21} \\ - \frac{47}{7} & - \frac{18}{7} \end{array} |$ .

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Step 3.1

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

$- \frac{9}{7} \cdot \frac{2}{7} - \frac{1}{7} (\frac{40}{21} (- \frac{18}{7}) - (- \frac{47}{7} \cdot \frac{11}{21})) - \frac{3}{7} | \begin{array}{c} \frac{40}{21} & - \frac{2}{7} \\ - \frac{47}{7} & \frac{6}{7} \end{array} |$

Step 3.2

Simplify the determinant.

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Step 3.2.1

Simplify each term.

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Step 3.2.1.1

Cancel the common factor of $3$ .

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Step 3.2.1.1.1

Move the leading negative in $- \frac{18}{7}$ into the numerator.

$- \frac{9}{7} \cdot \frac{2}{7} - \frac{1}{7} (\frac{40}{21} \cdot \frac{- 18}{7} - (- \frac{47}{7} \cdot \frac{11}{21})) - \frac{3}{7} | \begin{array}{c} \frac{40}{21} & - \frac{2}{7} \\ - \frac{47}{7} & \frac{6}{7} \end{array} |$

Step 3.2.1.1.2

Factor $3$ out of $21$ .

$- \frac{9}{7} \cdot \frac{2}{7} - \frac{1}{7} (\frac{40}{3 (7)} \cdot \frac{- 18}{7} - (- \frac{47}{7} \cdot \frac{11}{21})) - \frac{3}{7} | \begin{array}{c} \frac{40}{21} & - \frac{2}{7} \\ - \frac{47}{7} & \frac{6}{7} \end{array} |$

Step 3.2.1.1.3

Factor $3$ out of $- 18$ .

$- \frac{9}{7} \cdot \frac{2}{7} - \frac{1}{7} (\frac{40}{3 \cdot 7} \cdot \frac{3 \cdot - 6}{7} - (- \frac{47}{7} \cdot \frac{11}{21})) - \frac{3}{7} | \begin{array}{c} \frac{40}{21} & - \frac{2}{7} \\ - \frac{47}{7} & \frac{6}{7} \end{array} |$

Step 3.2.1.1.4

Cancel the common factor.

Step 3.2.1.1.5

Rewrite the expression.

$- \frac{9}{7} \cdot \frac{2}{7} - \frac{1}{7} (\frac{40}{7} \cdot \frac{- 6}{7} - (- \frac{47}{7} \cdot \frac{11}{21})) - \frac{3}{7} | \begin{array}{c} \frac{40}{21} & - \frac{2}{7} \\ - \frac{47}{7} & \frac{6}{7} \end{array} |$

Step 3.2.1.2

Multiply $\frac{40}{7}$ by $\frac{- 6}{7}$ .

$- \frac{9}{7} \cdot \frac{2}{7} - \frac{1}{7} (\frac{40 \cdot - 6}{7 \cdot 7} - (- \frac{47}{7} \cdot \frac{11}{21})) - \frac{3}{7} | \begin{array}{c} \frac{40}{21} & - \frac{2}{7} \\ - \frac{47}{7} & \frac{6}{7} \end{array} |$

Step 3.2.1.3

Multiply $40$ by $- 6$ .

$- \frac{9}{7} \cdot \frac{2}{7} - \frac{1}{7} (\frac{- 240}{7 \cdot 7} - (- \frac{47}{7} \cdot \frac{11}{21})) - \frac{3}{7} | \begin{array}{c} \frac{40}{21} & - \frac{2}{7} \\ - \frac{47}{7} & \frac{6}{7} \end{array} |$

Step 3.2.1.4

Multiply $7$ by $7$ .

$- \frac{9}{7} \cdot \frac{2}{7} - \frac{1}{7} (\frac{- 240}{49} - (- \frac{47}{7} \cdot \frac{11}{21})) - \frac{3}{7} | \begin{array}{c} \frac{40}{21} & - \frac{2}{7} \\ - \frac{47}{7} & \frac{6}{7} \end{array} |$

Step 3.2.1.5

Move the negative in front of the fraction.

$- \frac{9}{7} \cdot \frac{2}{7} - \frac{1}{7} (- \frac{240}{49} - (- \frac{47}{7} \cdot \frac{11}{21})) - \frac{3}{7} | \begin{array}{c} \frac{40}{21} & - \frac{2}{7} \\ - \frac{47}{7} & \frac{6}{7} \end{array} |$

Step 3.2.1.6

Multiply $- \frac{47}{7} \cdot \frac{11}{21}$ .

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Step 3.2.1.6.1

Multiply $\frac{11}{21}$ by $\frac{47}{7}$ .

$- \frac{9}{7} \cdot \frac{2}{7} - \frac{1}{7} (- \frac{240}{49} - - \frac{11 \cdot 47}{21 \cdot 7}) - \frac{3}{7} | \begin{array}{c} \frac{40}{21} & - \frac{2}{7} \\ - \frac{47}{7} & \frac{6}{7} \end{array} |$

Step 3.2.1.6.2

Multiply $11$ by $47$ .

$- \frac{9}{7} \cdot \frac{2}{7} - \frac{1}{7} (- \frac{240}{49} - - \frac{517}{21 \cdot 7}) - \frac{3}{7} | \begin{array}{c} \frac{40}{21} & - \frac{2}{7} \\ - \frac{47}{7} & \frac{6}{7} \end{array} |$

Step 3.2.1.6.3

Multiply $21$ by $7$ .

$- \frac{9}{7} \cdot \frac{2}{7} - \frac{1}{7} (- \frac{240}{49} - - \frac{517}{147}) - \frac{3}{7} | \begin{array}{c} \frac{40}{21} & - \frac{2}{7} \\ - \frac{47}{7} & \frac{6}{7} \end{array} |$

Step 3.2.1.7

Multiply $- - \frac{517}{147}$ .

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Step 3.2.1.7.1

Multiply $- 1$ by $- 1$ .

$- \frac{9}{7} \cdot \frac{2}{7} - \frac{1}{7} (- \frac{240}{49} + 1 (\frac{517}{147})) - \frac{3}{7} | \begin{array}{c} \frac{40}{21} & - \frac{2}{7} \\ - \frac{47}{7} & \frac{6}{7} \end{array} |$

Step 3.2.1.7.2

Multiply $\frac{517}{147}$ by $1$ .

$- \frac{9}{7} \cdot \frac{2}{7} - \frac{1}{7} (- \frac{240}{49} + \frac{517}{147}) - \frac{3}{7} | \begin{array}{c} \frac{40}{21} & - \frac{2}{7} \\ - \frac{47}{7} & \frac{6}{7} \end{array} |$

Step 3.2.2

To write $- \frac{240}{49}$ as a fraction with a common denominator, multiply by $\frac{3}{3}$ .

$- \frac{9}{7} \cdot \frac{2}{7} - \frac{1}{7} (- \frac{240}{49} \cdot \frac{3}{3} + \frac{517}{147}) - \frac{3}{7} | \begin{array}{c} \frac{40}{21} & - \frac{2}{7} \\ - \frac{47}{7} & \frac{6}{7} \end{array} |$

Step 3.2.3

Write each expression with a common denominator of $147$ , by multiplying each by an appropriate factor of $1$ .

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Step 3.2.3.1

Multiply $\frac{240}{49}$ by $\frac{3}{3}$ .

$- \frac{9}{7} \cdot \frac{2}{7} - \frac{1}{7} (- \frac{240 \cdot 3}{49 \cdot 3} + \frac{517}{147}) - \frac{3}{7} | \begin{array}{c} \frac{40}{21} & - \frac{2}{7} \\ - \frac{47}{7} & \frac{6}{7} \end{array} |$

Step 3.2.3.2

Multiply $49$ by $3$ .

$- \frac{9}{7} \cdot \frac{2}{7} - \frac{1}{7} (- \frac{240 \cdot 3}{147} + \frac{517}{147}) - \frac{3}{7} | \begin{array}{c} \frac{40}{21} & - \frac{2}{7} \\ - \frac{47}{7} & \frac{6}{7} \end{array} |$

Step 3.2.4

Combine the numerators over the common denominator.

$- \frac{9}{7} \cdot \frac{2}{7} - \frac{1}{7} \cdot \frac{- 240 \cdot 3 + 517}{147} - \frac{3}{7} | \begin{array}{c} \frac{40}{21} & - \frac{2}{7} \\ - \frac{47}{7} & \frac{6}{7} \end{array} |$

Step 3.2.5

Simplify the numerator.

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Step 3.2.5.1

Multiply $- 240$ by $3$ .

$- \frac{9}{7} \cdot \frac{2}{7} - \frac{1}{7} \cdot \frac{- 720 + 517}{147} - \frac{3}{7} | \begin{array}{c} \frac{40}{21} & - \frac{2}{7} \\ - \frac{47}{7} & \frac{6}{7} \end{array} |$

Step 3.2.5.2

Add $- 720$ and $517$ .

$- \frac{9}{7} \cdot \frac{2}{7} - \frac{1}{7} \cdot \frac{- 203}{147} - \frac{3}{7} | \begin{array}{c} \frac{40}{21} & - \frac{2}{7} \\ - \frac{47}{7} & \frac{6}{7} \end{array} |$

Step 3.2.6

Cancel the common factor of $- 203$ and $147$ .

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Step 3.2.6.1

Factor $7$ out of $- 203$ .

$- \frac{9}{7} \cdot \frac{2}{7} - \frac{1}{7} \cdot \frac{7 (- 29)}{147} - \frac{3}{7} | \begin{array}{c} \frac{40}{21} & - \frac{2}{7} \\ - \frac{47}{7} & \frac{6}{7} \end{array} |$

Step 3.2.6.2

Cancel the common factors.

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Step 3.2.6.2.1

Factor $7$ out of $147$ .

$- \frac{9}{7} \cdot \frac{2}{7} - \frac{1}{7} \cdot \frac{7 \cdot - 29}{7 \cdot 21} - \frac{3}{7} | \begin{array}{c} \frac{40}{21} & - \frac{2}{7} \\ - \frac{47}{7} & \frac{6}{7} \end{array} |$

Step 3.2.6.2.2

Cancel the common factor.

$- \frac{9}{7} \cdot \frac{2}{7} - \frac{1}{7} \cdot \frac{7 \cdot - 29}{7 \cdot 21} - \frac{3}{7} | \begin{array}{c} \frac{40}{21} & - \frac{2}{7} \\ - \frac{47}{7} & \frac{6}{7} \end{array} |$

Step 3.2.6.2.3

Rewrite the expression.

$- \frac{9}{7} \cdot \frac{2}{7} - \frac{1}{7} \cdot \frac{- 29}{21} - \frac{3}{7} | \begin{array}{c} \frac{40}{21} & - \frac{2}{7} \\ - \frac{47}{7} & \frac{6}{7} \end{array} |$

Step 3.2.7

Move the negative in front of the fraction.

$- \frac{9}{7} \cdot \frac{2}{7} - \frac{1}{7} (- \frac{29}{21}) - \frac{3}{7} | \begin{array}{c} \frac{40}{21} & - \frac{2}{7} \\ - \frac{47}{7} & \frac{6}{7} \end{array} |$

Step 4

Evaluate $| \begin{array}{c} \frac{40}{21} & - \frac{2}{7} \\ - \frac{47}{7} & \frac{6}{7} \end{array} |$ .

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Step 4.1

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

$- \frac{9}{7} \cdot \frac{2}{7} - \frac{1}{7} (- \frac{29}{21}) - \frac{3}{7} (\frac{40}{21} \cdot \frac{6}{7} - (- \frac{47}{7} (- \frac{2}{7})))$

Step 4.2

Simplify the determinant.

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Step 4.2.1

Simplify each term.

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Step 4.2.1.1

Cancel the common factor of $3$ .

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Step 4.2.1.1.1

Factor $3$ out of $21$ .

$- \frac{9}{7} \cdot \frac{2}{7} - \frac{1}{7} (- \frac{29}{21}) - \frac{3}{7} (\frac{40}{3 (7)} \cdot \frac{6}{7} - (- \frac{47}{7} (- \frac{2}{7})))$

Step 4.2.1.1.2

Factor $3$ out of $6$ .

$- \frac{9}{7} \cdot \frac{2}{7} - \frac{1}{7} (- \frac{29}{21}) - \frac{3}{7} (\frac{40}{3 \cdot 7} \cdot \frac{3 \cdot 2}{7} - (- \frac{47}{7} (- \frac{2}{7})))$

Step 4.2.1.1.3

Cancel the common factor.

$- \frac{9}{7} \cdot \frac{2}{7} - \frac{1}{7} (- \frac{29}{21}) - \frac{3}{7} (\frac{40}{3 \cdot 7} \cdot \frac{3 \cdot 2}{7} - (- \frac{47}{7} (- \frac{2}{7})))$

Step 4.2.1.1.4

Rewrite the expression.

$- \frac{9}{7} \cdot \frac{2}{7} - \frac{1}{7} (- \frac{29}{21}) - \frac{3}{7} (\frac{40}{7} \cdot \frac{2}{7} - (- \frac{47}{7} (- \frac{2}{7})))$

Step 4.2.1.2

Multiply $\frac{40}{7}$ by $\frac{2}{7}$ .

$- \frac{9}{7} \cdot \frac{2}{7} - \frac{1}{7} (- \frac{29}{21}) - \frac{3}{7} (\frac{40 \cdot 2}{7 \cdot 7} - (- \frac{47}{7} (- \frac{2}{7})))$

Step 4.2.1.3

Multiply $40$ by $2$ .

$- \frac{9}{7} \cdot \frac{2}{7} - \frac{1}{7} (- \frac{29}{21}) - \frac{3}{7} (\frac{80}{7 \cdot 7} - (- \frac{47}{7} (- \frac{2}{7})))$

Step 4.2.1.4

Multiply $7$ by $7$ .

$- \frac{9}{7} \cdot \frac{2}{7} - \frac{1}{7} (- \frac{29}{21}) - \frac{3}{7} (\frac{80}{49} - (- \frac{47}{7} (- \frac{2}{7})))$

Step 4.2.1.5

Multiply $- \frac{47}{7} (- \frac{2}{7})$ .

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Step 4.2.1.5.1

Multiply $- 1$ by $- 1$ .

$- \frac{9}{7} \cdot \frac{2}{7} - \frac{1}{7} (- \frac{29}{21}) - \frac{3}{7} (\frac{80}{49} - (1 (\frac{47}{7}) \frac{2}{7}))$

Step 4.2.1.5.2

Multiply $\frac{47}{7}$ by $1$ .

$- \frac{9}{7} \cdot \frac{2}{7} - \frac{1}{7} (- \frac{29}{21}) - \frac{3}{7} (\frac{80}{49} - (\frac{47}{7} \cdot \frac{2}{7}))$

Step 4.2.1.5.3

Multiply $\frac{47}{7}$ by $\frac{2}{7}$ .

$- \frac{9}{7} \cdot \frac{2}{7} - \frac{1}{7} (- \frac{29}{21}) - \frac{3}{7} (\frac{80}{49} - \frac{47 \cdot 2}{7 \cdot 7})$

Step 4.2.1.5.4

Multiply $47$ by $2$ .

$- \frac{9}{7} \cdot \frac{2}{7} - \frac{1}{7} (- \frac{29}{21}) - \frac{3}{7} (\frac{80}{49} - \frac{94}{7 \cdot 7})$

Step 4.2.1.5.5

Multiply $7$ by $7$ .

$- \frac{9}{7} \cdot \frac{2}{7} - \frac{1}{7} (- \frac{29}{21}) - \frac{3}{7} (\frac{80}{49} - \frac{94}{49})$

Step 4.2.2

Combine the numerators over the common denominator.

$- \frac{9}{7} \cdot \frac{2}{7} - \frac{1}{7} (- \frac{29}{21}) - \frac{3}{7} \cdot \frac{80 - 94}{49}$

Step 4.2.3

Subtract $94$ from $80$ .

$- \frac{9}{7} \cdot \frac{2}{7} - \frac{1}{7} (- \frac{29}{21}) - \frac{3}{7} \cdot \frac{- 14}{49}$

Step 4.2.4

Cancel the common factor of $- 14$ and $49$ .

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Step 4.2.4.1

Factor $7$ out of $- 14$ .

$- \frac{9}{7} \cdot \frac{2}{7} - \frac{1}{7} (- \frac{29}{21}) - \frac{3}{7} \cdot \frac{7 (- 2)}{49}$

Step 4.2.4.2

Cancel the common factors.

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Step 4.2.4.2.1

Factor $7$ out of $49$ .

$- \frac{9}{7} \cdot \frac{2}{7} - \frac{1}{7} (- \frac{29}{21}) - \frac{3}{7} \cdot \frac{7 \cdot - 2}{7 \cdot 7}$

Step 4.2.4.2.2

Cancel the common factor.

$- \frac{9}{7} \cdot \frac{2}{7} - \frac{1}{7} (- \frac{29}{21}) - \frac{3}{7} \cdot \frac{7 \cdot - 2}{7 \cdot 7}$

Step 4.2.4.2.3

Rewrite the expression.

$- \frac{9}{7} \cdot \frac{2}{7} - \frac{1}{7} (- \frac{29}{21}) - \frac{3}{7} \cdot \frac{- 2}{7}$

Step 4.2.5

Move the negative in front of the fraction.

$- \frac{9}{7} \cdot \frac{2}{7} - \frac{1}{7} (- \frac{29}{21}) - \frac{3}{7} (- \frac{2}{7})$

Step 5

Simplify the determinant.

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Step 5.1

Simplify each term.

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Step 5.1.1

Multiply $- \frac{9}{7} \cdot \frac{2}{7}$ .

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Step 5.1.1.1

Multiply $\frac{2}{7}$ by $\frac{9}{7}$ .

$- \frac{2 \cdot 9}{7 \cdot 7} - \frac{1}{7} (- \frac{29}{21}) - \frac{3}{7} (- \frac{2}{7})$

Step 5.1.1.2

Multiply $2$ by $9$ .

$- \frac{18}{7 \cdot 7} - \frac{1}{7} (- \frac{29}{21}) - \frac{3}{7} (- \frac{2}{7})$

Step 5.1.1.3

Multiply $7$ by $7$ .

$- \frac{18}{49} - \frac{1}{7} (- \frac{29}{21}) - \frac{3}{7} (- \frac{2}{7})$

Step 5.1.2

Multiply $- \frac{1}{7} (- \frac{29}{21})$ .

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Step 5.1.2.1

Multiply $- 1$ by $- 1$ .

$- \frac{18}{49} + 1 (\frac{1}{7}) \frac{29}{21} - \frac{3}{7} (- \frac{2}{7})$

Step 5.1.2.2

Multiply $\frac{1}{7}$ by $1$ .

$- \frac{18}{49} + \frac{1}{7} \cdot \frac{29}{21} - \frac{3}{7} (- \frac{2}{7})$

Step 5.1.2.3

Multiply $\frac{1}{7}$ by $\frac{29}{21}$ .

$- \frac{18}{49} + \frac{29}{7 \cdot 21} - \frac{3}{7} (- \frac{2}{7})$

Step 5.1.2.4

Multiply $7$ by $21$ .

$- \frac{18}{49} + \frac{29}{147} - \frac{3}{7} (- \frac{2}{7})$

Step 5.1.3

Multiply $- \frac{3}{7} (- \frac{2}{7})$ .

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Step 5.1.3.1

Multiply $- 1$ by $- 1$ .

$- \frac{18}{49} + \frac{29}{147} + 1 (\frac{3}{7}) \frac{2}{7}$

Step 5.1.3.2

Multiply $\frac{3}{7}$ by $1$ .

$- \frac{18}{49} + \frac{29}{147} + \frac{3}{7} \cdot \frac{2}{7}$

Step 5.1.3.3

Multiply $\frac{3}{7}$ by $\frac{2}{7}$ .

$- \frac{18}{49} + \frac{29}{147} + \frac{3 \cdot 2}{7 \cdot 7}$

Step 5.1.3.4

Multiply $3$ by $2$ .

$- \frac{18}{49} + \frac{29}{147} + \frac{6}{7 \cdot 7}$

Step 5.1.3.5

Multiply $7$ by $7$ .

$- \frac{18}{49} + \frac{29}{147} + \frac{6}{49}$

Step 5.2

Combine the numerators over the common denominator.

$\frac{- 18 + 6}{49} + \frac{29}{147}$

Step 5.3

Add $- 18$ and $6$ .

$\frac{- 12}{49} + \frac{29}{147}$

Step 5.4

Move the negative in front of the fraction.

$- \frac{12}{49} + \frac{29}{147}$

Step 5.5

To write $- \frac{12}{49}$ as a fraction with a common denominator, multiply by $\frac{3}{3}$ .

$- \frac{12}{49} \cdot \frac{3}{3} + \frac{29}{147}$

Step 5.6

Write each expression with a common denominator of $147$ , by multiplying each by an appropriate factor of $1$ .

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Step 5.6.1

Multiply $\frac{12}{49}$ by $\frac{3}{3}$ .

$- \frac{12 \cdot 3}{49 \cdot 3} + \frac{29}{147}$

Step 5.6.2

Multiply $49$ by $3$ .

$- \frac{12 \cdot 3}{147} + \frac{29}{147}$

Step 5.7

Combine the numerators over the common denominator.

$\frac{- 12 \cdot 3 + 29}{147}$

Step 5.8

Simplify the numerator.

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Step 5.8.1

Multiply $- 12$ by $3$ .

$\frac{- 36 + 29}{147}$

Step 5.8.2

Add $- 36$ and $29$ .

$\frac{- 7}{147}$

Step 5.9

Cancel the common factor of $- 7$ and $147$ .

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Step 5.9.1

Factor $7$ out of $- 7$ .

$\frac{7 (- 1)}{147}$

Step 5.9.2

Cancel the common factors.

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Step 5.9.2.1

Factor $7$ out of $147$ .

$\frac{7 \cdot - 1}{7 \cdot 21}$

Step 5.9.2.2

Cancel the common factor.

$\frac{7 \cdot - 1}{7 \cdot 21}$

Step 5.9.2.3

Rewrite the expression.

$\frac{- 1}{21}$

Step 5.10

Move the negative in front of the fraction.

$- \frac{1}{21}$