Linear Algebra Examples

$[\begin{array}{c} \frac{1}{11} & \frac{1}{11} & - \frac{5}{11} \\ \frac{1}{11} & \frac{1}{11} & \frac{1}{22} \\ \frac{1}{11} & - \frac{10}{11} & \frac{1}{22} \end{array}]$

Step 1

Find the determinant.

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Step 1.1

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 1.1.1

Consider the corresponding sign chart.

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

Step 1.1.2

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

Step 1.1.3

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

$| \begin{array}{c} \frac{1}{11} & \frac{1}{22} \\ - \frac{10}{11} & \frac{1}{22} \end{array} |$

Step 1.1.4

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

$\frac{1}{11} | \begin{array}{c} \frac{1}{11} & \frac{1}{22} \\ - \frac{10}{11} & \frac{1}{22} \end{array} |$

Step 1.1.5

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

$| \begin{array}{c} \frac{1}{11} & \frac{1}{22} \\ \frac{1}{11} & \frac{1}{22} \end{array} |$

Step 1.1.6

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

$- \frac{1}{11} | \begin{array}{c} \frac{1}{11} & \frac{1}{22} \\ \frac{1}{11} & \frac{1}{22} \end{array} |$

Step 1.1.7

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

$| \begin{array}{c} \frac{1}{11} & \frac{1}{11} \\ \frac{1}{11} & - \frac{10}{11} \end{array} |$

Step 1.1.8

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

$- \frac{5}{11} | \begin{array}{c} \frac{1}{11} & \frac{1}{11} \\ \frac{1}{11} & - \frac{10}{11} \end{array} |$

Step 1.1.9

Add the terms together.

$\frac{1}{11} | \begin{array}{c} \frac{1}{11} & \frac{1}{22} \\ - \frac{10}{11} & \frac{1}{22} \end{array} | - \frac{1}{11} | \begin{array}{c} \frac{1}{11} & \frac{1}{22} \\ \frac{1}{11} & \frac{1}{22} \end{array} | - \frac{5}{11} | \begin{array}{c} \frac{1}{11} & \frac{1}{11} \\ \frac{1}{11} & - \frac{10}{11} \end{array} |$

Step 1.2

Evaluate $| \begin{array}{c} \frac{1}{11} & \frac{1}{22} \\ - \frac{10}{11} & \frac{1}{22} \end{array} |$ .

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Step 1.2.1

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

$\frac{1}{11} (\frac{1}{11} \cdot \frac{1}{22} - (- \frac{10}{11} \cdot \frac{1}{22})) - \frac{1}{11} | \begin{array}{c} \frac{1}{11} & \frac{1}{22} \\ \frac{1}{11} & \frac{1}{22} \end{array} | - \frac{5}{11} | \begin{array}{c} \frac{1}{11} & \frac{1}{11} \\ \frac{1}{11} & - \frac{10}{11} \end{array} |$

Step 1.2.2

Simplify the determinant.

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Step 1.2.2.1

Simplify each term.

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Step 1.2.2.1.1

Multiply $\frac{1}{11} \cdot \frac{1}{22}$ .

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Step 1.2.2.1.1.1

Multiply $\frac{1}{11}$ by $\frac{1}{22}$ .

$\frac{1}{11} (\frac{1}{11 \cdot 22} - (- \frac{10}{11} \cdot \frac{1}{22})) - \frac{1}{11} | \begin{array}{c} \frac{1}{11} & \frac{1}{22} \\ \frac{1}{11} & \frac{1}{22} \end{array} | - \frac{5}{11} | \begin{array}{c} \frac{1}{11} & \frac{1}{11} \\ \frac{1}{11} & - \frac{10}{11} \end{array} |$

Step 1.2.2.1.1.2

Multiply $11$ by $22$ .

$\frac{1}{11} (\frac{1}{242} - (- \frac{10}{11} \cdot \frac{1}{22})) - \frac{1}{11} | \begin{array}{c} \frac{1}{11} & \frac{1}{22} \\ \frac{1}{11} & \frac{1}{22} \end{array} | - \frac{5}{11} | \begin{array}{c} \frac{1}{11} & \frac{1}{11} \\ \frac{1}{11} & - \frac{10}{11} \end{array} |$

Step 1.2.2.1.2

Cancel the common factor of $2$ .

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Step 1.2.2.1.2.1

Move the leading negative in $- \frac{10}{11}$ into the numerator.

$\frac{1}{11} (\frac{1}{242} - (\frac{- 10}{11} \cdot \frac{1}{22})) - \frac{1}{11} | \begin{array}{c} \frac{1}{11} & \frac{1}{22} \\ \frac{1}{11} & \frac{1}{22} \end{array} | - \frac{5}{11} | \begin{array}{c} \frac{1}{11} & \frac{1}{11} \\ \frac{1}{11} & - \frac{10}{11} \end{array} |$

Step 1.2.2.1.2.2

Factor $2$ out of $- 10$ .

$\frac{1}{11} (\frac{1}{242} - (\frac{2 (- 5)}{11} \cdot \frac{1}{22})) - \frac{1}{11} | \begin{array}{c} \frac{1}{11} & \frac{1}{22} \\ \frac{1}{11} & \frac{1}{22} \end{array} | - \frac{5}{11} | \begin{array}{c} \frac{1}{11} & \frac{1}{11} \\ \frac{1}{11} & - \frac{10}{11} \end{array} |$

Step 1.2.2.1.2.3

Factor $2$ out of $22$ .

$\frac{1}{11} (\frac{1}{242} - (\frac{2 \cdot - 5}{11} \cdot \frac{1}{2 \cdot 11})) - \frac{1}{11} | \begin{array}{c} \frac{1}{11} & \frac{1}{22} \\ \frac{1}{11} & \frac{1}{22} \end{array} | - \frac{5}{11} | \begin{array}{c} \frac{1}{11} & \frac{1}{11} \\ \frac{1}{11} & - \frac{10}{11} \end{array} |$

Step 1.2.2.1.2.4

Cancel the common factor.

Step 1.2.2.1.2.5

Rewrite the expression.

$\frac{1}{11} (\frac{1}{242} - (\frac{- 5}{11} \cdot \frac{1}{11})) - \frac{1}{11} | \begin{array}{c} \frac{1}{11} & \frac{1}{22} \\ \frac{1}{11} & \frac{1}{22} \end{array} | - \frac{5}{11} | \begin{array}{c} \frac{1}{11} & \frac{1}{11} \\ \frac{1}{11} & - \frac{10}{11} \end{array} |$

Step 1.2.2.1.3

Multiply $\frac{- 5}{11}$ by $\frac{1}{11}$ .

$\frac{1}{11} (\frac{1}{242} - \frac{- 5}{11 \cdot 11}) - \frac{1}{11} | \begin{array}{c} \frac{1}{11} & \frac{1}{22} \\ \frac{1}{11} & \frac{1}{22} \end{array} | - \frac{5}{11} | \begin{array}{c} \frac{1}{11} & \frac{1}{11} \\ \frac{1}{11} & - \frac{10}{11} \end{array} |$

Step 1.2.2.1.4

Multiply $11$ by $11$ .

$\frac{1}{11} (\frac{1}{242} - \frac{- 5}{121}) - \frac{1}{11} | \begin{array}{c} \frac{1}{11} & \frac{1}{22} \\ \frac{1}{11} & \frac{1}{22} \end{array} | - \frac{5}{11} | \begin{array}{c} \frac{1}{11} & \frac{1}{11} \\ \frac{1}{11} & - \frac{10}{11} \end{array} |$

Step 1.2.2.1.5

Move the negative in front of the fraction.

$\frac{1}{11} (\frac{1}{242} - - \frac{5}{121}) - \frac{1}{11} | \begin{array}{c} \frac{1}{11} & \frac{1}{22} \\ \frac{1}{11} & \frac{1}{22} \end{array} | - \frac{5}{11} | \begin{array}{c} \frac{1}{11} & \frac{1}{11} \\ \frac{1}{11} & - \frac{10}{11} \end{array} |$

Step 1.2.2.1.6

Multiply $- - \frac{5}{121}$ .

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Step 1.2.2.1.6.1

Multiply $- 1$ by $- 1$ .

$\frac{1}{11} (\frac{1}{242} + 1 (\frac{5}{121})) - \frac{1}{11} | \begin{array}{c} \frac{1}{11} & \frac{1}{22} \\ \frac{1}{11} & \frac{1}{22} \end{array} | - \frac{5}{11} | \begin{array}{c} \frac{1}{11} & \frac{1}{11} \\ \frac{1}{11} & - \frac{10}{11} \end{array} |$

Step 1.2.2.1.6.2

Multiply $\frac{5}{121}$ by $1$ .

$\frac{1}{11} (\frac{1}{242} + \frac{5}{121}) - \frac{1}{11} | \begin{array}{c} \frac{1}{11} & \frac{1}{22} \\ \frac{1}{11} & \frac{1}{22} \end{array} | - \frac{5}{11} | \begin{array}{c} \frac{1}{11} & \frac{1}{11} \\ \frac{1}{11} & - \frac{10}{11} \end{array} |$

Step 1.2.2.2

To write $\frac{5}{121}$ as a fraction with a common denominator, multiply by $\frac{2}{2}$ .

$\frac{1}{11} (\frac{1}{242} + \frac{5}{121} \cdot \frac{2}{2}) - \frac{1}{11} | \begin{array}{c} \frac{1}{11} & \frac{1}{22} \\ \frac{1}{11} & \frac{1}{22} \end{array} | - \frac{5}{11} | \begin{array}{c} \frac{1}{11} & \frac{1}{11} \\ \frac{1}{11} & - \frac{10}{11} \end{array} |$

Step 1.2.2.3

Write each expression with a common denominator of $242$ , by multiplying each by an appropriate factor of $1$ .

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Step 1.2.2.3.1

Multiply $\frac{5}{121}$ by $\frac{2}{2}$ .

$\frac{1}{11} (\frac{1}{242} + \frac{5 \cdot 2}{121 \cdot 2}) - \frac{1}{11} | \begin{array}{c} \frac{1}{11} & \frac{1}{22} \\ \frac{1}{11} & \frac{1}{22} \end{array} | - \frac{5}{11} | \begin{array}{c} \frac{1}{11} & \frac{1}{11} \\ \frac{1}{11} & - \frac{10}{11} \end{array} |$

Step 1.2.2.3.2

Multiply $121$ by $2$ .

$\frac{1}{11} (\frac{1}{242} + \frac{5 \cdot 2}{242}) - \frac{1}{11} | \begin{array}{c} \frac{1}{11} & \frac{1}{22} \\ \frac{1}{11} & \frac{1}{22} \end{array} | - \frac{5}{11} | \begin{array}{c} \frac{1}{11} & \frac{1}{11} \\ \frac{1}{11} & - \frac{10}{11} \end{array} |$

Step 1.2.2.4

Combine the numerators over the common denominator.

$\frac{1}{11} \cdot \frac{1 + 5 \cdot 2}{242} - \frac{1}{11} | \begin{array}{c} \frac{1}{11} & \frac{1}{22} \\ \frac{1}{11} & \frac{1}{22} \end{array} | - \frac{5}{11} | \begin{array}{c} \frac{1}{11} & \frac{1}{11} \\ \frac{1}{11} & - \frac{10}{11} \end{array} |$

Step 1.2.2.5

Simplify the numerator.

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Step 1.2.2.5.1

Multiply $5$ by $2$ .

$\frac{1}{11} \cdot \frac{1 + 10}{242} - \frac{1}{11} | \begin{array}{c} \frac{1}{11} & \frac{1}{22} \\ \frac{1}{11} & \frac{1}{22} \end{array} | - \frac{5}{11} | \begin{array}{c} \frac{1}{11} & \frac{1}{11} \\ \frac{1}{11} & - \frac{10}{11} \end{array} |$

Step 1.2.2.5.2

Add $1$ and $10$ .

$\frac{1}{11} \cdot \frac{11}{242} - \frac{1}{11} | \begin{array}{c} \frac{1}{11} & \frac{1}{22} \\ \frac{1}{11} & \frac{1}{22} \end{array} | - \frac{5}{11} | \begin{array}{c} \frac{1}{11} & \frac{1}{11} \\ \frac{1}{11} & - \frac{10}{11} \end{array} |$

Step 1.2.2.6

Cancel the common factor of $11$ and $242$ .

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Step 1.2.2.6.1

Factor $11$ out of $11$ .

$\frac{1}{11} \cdot \frac{11 (1)}{242} - \frac{1}{11} | \begin{array}{c} \frac{1}{11} & \frac{1}{22} \\ \frac{1}{11} & \frac{1}{22} \end{array} | - \frac{5}{11} | \begin{array}{c} \frac{1}{11} & \frac{1}{11} \\ \frac{1}{11} & - \frac{10}{11} \end{array} |$

Step 1.2.2.6.2

Cancel the common factors.

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Step 1.2.2.6.2.1

Factor $11$ out of $242$ .

$\frac{1}{11} \cdot \frac{11 \cdot 1}{11 \cdot 22} - \frac{1}{11} | \begin{array}{c} \frac{1}{11} & \frac{1}{22} \\ \frac{1}{11} & \frac{1}{22} \end{array} | - \frac{5}{11} | \begin{array}{c} \frac{1}{11} & \frac{1}{11} \\ \frac{1}{11} & - \frac{10}{11} \end{array} |$

Step 1.2.2.6.2.2

Cancel the common factor.

Step 1.2.2.6.2.3

Rewrite the expression.

$\frac{1}{11} \cdot \frac{1}{22} - \frac{1}{11} | \begin{array}{c} \frac{1}{11} & \frac{1}{22} \\ \frac{1}{11} & \frac{1}{22} \end{array} | - \frac{5}{11} | \begin{array}{c} \frac{1}{11} & \frac{1}{11} \\ \frac{1}{11} & - \frac{10}{11} \end{array} |$

Step 1.3

Evaluate $| \begin{array}{c} \frac{1}{11} & \frac{1}{22} \\ \frac{1}{11} & \frac{1}{22} \end{array} |$ .

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Step 1.3.1

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

$\frac{1}{11} \cdot \frac{1}{22} - \frac{1}{11} (\frac{1}{11} \cdot \frac{1}{22} - \frac{1}{11} \cdot \frac{1}{22}) - \frac{5}{11} | \begin{array}{c} \frac{1}{11} & \frac{1}{11} \\ \frac{1}{11} & - \frac{10}{11} \end{array} |$

Step 1.3.2

Simplify the determinant.

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Step 1.3.2.1

Simplify each term.

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Step 1.3.2.1.1

Multiply $\frac{1}{11} \cdot \frac{1}{22}$ .

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Step 1.3.2.1.1.1

Multiply $\frac{1}{11}$ by $\frac{1}{22}$ .

$\frac{1}{11} \cdot \frac{1}{22} - \frac{1}{11} (\frac{1}{11 \cdot 22} - \frac{1}{11} \cdot \frac{1}{22}) - \frac{5}{11} | \begin{array}{c} \frac{1}{11} & \frac{1}{11} \\ \frac{1}{11} & - \frac{10}{11} \end{array} |$

Step 1.3.2.1.1.2

Multiply $11$ by $22$ .

$\frac{1}{11} \cdot \frac{1}{22} - \frac{1}{11} (\frac{1}{242} - \frac{1}{11} \cdot \frac{1}{22}) - \frac{5}{11} | \begin{array}{c} \frac{1}{11} & \frac{1}{11} \\ \frac{1}{11} & - \frac{10}{11} \end{array} |$

Step 1.3.2.1.2

Multiply $- \frac{1}{11} \cdot \frac{1}{22}$ .

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Step 1.3.2.1.2.1

Multiply $\frac{1}{22}$ by $\frac{1}{11}$ .

$\frac{1}{11} \cdot \frac{1}{22} - \frac{1}{11} (\frac{1}{242} - \frac{1}{22 \cdot 11}) - \frac{5}{11} | \begin{array}{c} \frac{1}{11} & \frac{1}{11} \\ \frac{1}{11} & - \frac{10}{11} \end{array} |$

Step 1.3.2.1.2.2

Multiply $22$ by $11$ .

$\frac{1}{11} \cdot \frac{1}{22} - \frac{1}{11} (\frac{1}{242} - \frac{1}{242}) - \frac{5}{11} | \begin{array}{c} \frac{1}{11} & \frac{1}{11} \\ \frac{1}{11} & - \frac{10}{11} \end{array} |$

Step 1.3.2.2

Combine the numerators over the common denominator.

$\frac{1}{11} \cdot \frac{1}{22} - \frac{1}{11} \cdot \frac{1 - 1}{242} - \frac{5}{11} | \begin{array}{c} \frac{1}{11} & \frac{1}{11} \\ \frac{1}{11} & - \frac{10}{11} \end{array} |$

Step 1.3.2.3

Subtract $1$ from $1$ .

$\frac{1}{11} \cdot \frac{1}{22} - \frac{1}{11} \cdot \frac{0}{242} - \frac{5}{11} | \begin{array}{c} \frac{1}{11} & \frac{1}{11} \\ \frac{1}{11} & - \frac{10}{11} \end{array} |$

Step 1.3.2.4

Divide $0$ by $242$ .

$\frac{1}{11} \cdot \frac{1}{22} - \frac{1}{11} \cdot 0 - \frac{5}{11} | \begin{array}{c} \frac{1}{11} & \frac{1}{11} \\ \frac{1}{11} & - \frac{10}{11} \end{array} |$

Step 1.4

Evaluate $| \begin{array}{c} \frac{1}{11} & \frac{1}{11} \\ \frac{1}{11} & - \frac{10}{11} \end{array} |$ .

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Step 1.4.1

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

$\frac{1}{11} \cdot \frac{1}{22} - \frac{1}{11} \cdot 0 - \frac{5}{11} (\frac{1}{11} (- \frac{10}{11}) - \frac{1}{11} \cdot \frac{1}{11})$

Step 1.4.2

Simplify the determinant.

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Step 1.4.2.1

Simplify each term.

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Step 1.4.2.1.1

Multiply $\frac{1}{11} (- \frac{10}{11})$ .

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Step 1.4.2.1.1.1

Multiply $\frac{1}{11}$ by $\frac{10}{11}$ .

$\frac{1}{11} \cdot \frac{1}{22} - \frac{1}{11} \cdot 0 - \frac{5}{11} (- \frac{10}{11 \cdot 11} - \frac{1}{11} \cdot \frac{1}{11})$

Step 1.4.2.1.1.2

Multiply $11$ by $11$ .

$\frac{1}{11} \cdot \frac{1}{22} - \frac{1}{11} \cdot 0 - \frac{5}{11} (- \frac{10}{121} - \frac{1}{11} \cdot \frac{1}{11})$

Step 1.4.2.1.2

Multiply $- \frac{1}{11} \cdot \frac{1}{11}$ .

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Step 1.4.2.1.2.1

Multiply $\frac{1}{11}$ by $\frac{1}{11}$ .

$\frac{1}{11} \cdot \frac{1}{22} - \frac{1}{11} \cdot 0 - \frac{5}{11} (- \frac{10}{121} - \frac{1}{11 \cdot 11})$

Step 1.4.2.1.2.2

Multiply $11$ by $11$ .

$\frac{1}{11} \cdot \frac{1}{22} - \frac{1}{11} \cdot 0 - \frac{5}{11} (- \frac{10}{121} - \frac{1}{121})$

Step 1.4.2.2

Combine the numerators over the common denominator.

$\frac{1}{11} \cdot \frac{1}{22} - \frac{1}{11} \cdot 0 - \frac{5}{11} \cdot \frac{- 10 - 1}{121}$

Step 1.4.2.3

Subtract $1$ from $- 10$ .

$\frac{1}{11} \cdot \frac{1}{22} - \frac{1}{11} \cdot 0 - \frac{5}{11} \cdot \frac{- 11}{121}$

Step 1.4.2.4

Cancel the common factor of $- 11$ and $121$ .

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Step 1.4.2.4.1

Factor $11$ out of $- 11$ .

$\frac{1}{11} \cdot \frac{1}{22} - \frac{1}{11} \cdot 0 - \frac{5}{11} \cdot \frac{11 (- 1)}{121}$

Step 1.4.2.4.2

Cancel the common factors.

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Step 1.4.2.4.2.1

Factor $11$ out of $121$ .

$\frac{1}{11} \cdot \frac{1}{22} - \frac{1}{11} \cdot 0 - \frac{5}{11} \cdot \frac{11 \cdot - 1}{11 \cdot 11}$

Step 1.4.2.4.2.2

Cancel the common factor.

$\frac{1}{11} \cdot \frac{1}{22} - \frac{1}{11} \cdot 0 - \frac{5}{11} \cdot \frac{11 \cdot - 1}{11 \cdot 11}$

Step 1.4.2.4.2.3

Rewrite the expression.

$\frac{1}{11} \cdot \frac{1}{22} - \frac{1}{11} \cdot 0 - \frac{5}{11} \cdot \frac{- 1}{11}$

Step 1.4.2.5

Move the negative in front of the fraction.

$\frac{1}{11} \cdot \frac{1}{22} - \frac{1}{11} \cdot 0 - \frac{5}{11} (- \frac{1}{11})$

Step 1.5

Simplify the determinant.

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Step 1.5.1

Simplify each term.

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Step 1.5.1.1

Multiply $\frac{1}{11} \cdot \frac{1}{22}$ .

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Step 1.5.1.1.1

Multiply $\frac{1}{11}$ by $\frac{1}{22}$ .

$\frac{1}{11 \cdot 22} - \frac{1}{11} \cdot 0 - \frac{5}{11} (- \frac{1}{11})$

Step 1.5.1.1.2

Multiply $11$ by $22$ .

$\frac{1}{242} - \frac{1}{11} \cdot 0 - \frac{5}{11} (- \frac{1}{11})$

Step 1.5.1.2

Multiply $- \frac{1}{11} \cdot 0$ .

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Step 1.5.1.2.1

Multiply $0$ by $- 1$ .

$\frac{1}{242} + 0 (\frac{1}{11}) - \frac{5}{11} (- \frac{1}{11})$

Step 1.5.1.2.2

Multiply $0$ by $\frac{1}{11}$ .

$\frac{1}{242} + 0 - \frac{5}{11} (- \frac{1}{11})$

Step 1.5.1.3

Multiply $- \frac{5}{11} (- \frac{1}{11})$ .

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Step 1.5.1.3.1

Multiply $- 1$ by $- 1$ .

$\frac{1}{242} + 0 + 1 (\frac{5}{11}) \frac{1}{11}$

Step 1.5.1.3.2

Multiply $\frac{5}{11}$ by $1$ .

$\frac{1}{242} + 0 + \frac{5}{11} \cdot \frac{1}{11}$

Step 1.5.1.3.3

Multiply $\frac{5}{11}$ by $\frac{1}{11}$ .

$\frac{1}{242} + 0 + \frac{5}{11 \cdot 11}$

Step 1.5.1.3.4

Multiply $11$ by $11$ .

$\frac{1}{242} + 0 + \frac{5}{121}$

Step 1.5.2

Add $\frac{1}{242}$ and $0$ .

$\frac{1}{242} + \frac{5}{121}$

Step 1.5.3

To write $\frac{5}{121}$ as a fraction with a common denominator, multiply by $\frac{2}{2}$ .

$\frac{1}{242} + \frac{5}{121} \cdot \frac{2}{2}$

Step 1.5.4

Write each expression with a common denominator of $242$ , by multiplying each by an appropriate factor of $1$ .

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Step 1.5.4.1

Multiply $\frac{5}{121}$ by $\frac{2}{2}$ .

$\frac{1}{242} + \frac{5 \cdot 2}{121 \cdot 2}$

Step 1.5.4.2

Multiply $121$ by $2$ .

$\frac{1}{242} + \frac{5 \cdot 2}{242}$

Step 1.5.5

Combine the numerators over the common denominator.

$\frac{1 + 5 \cdot 2}{242}$

Step 1.5.6

Simplify the numerator.

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Step 1.5.6.1

Multiply $5$ by $2$ .

$\frac{1 + 10}{242}$

Step 1.5.6.2

Add $1$ and $10$ .

$\frac{11}{242}$

Step 1.5.7

Cancel the common factor of $11$ and $242$ .

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Step 1.5.7.1

Factor $11$ out of $11$ .

$\frac{11 (1)}{242}$

Step 1.5.7.2

Cancel the common factors.

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Step 1.5.7.2.1

Factor $11$ out of $242$ .

$\frac{11 \cdot 1}{11 \cdot 22}$

Step 1.5.7.2.2

Cancel the common factor.

$\frac{11 \cdot 1}{11 \cdot 22}$

Step 1.5.7.2.3

Rewrite the expression.

$\frac{1}{22}$

Step 2

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

Step 3

Set up a $3 \times 6$ matrix where the left half is the original matrix and the right half is its identity matrix.

$[\begin{array}{c} \frac{1}{11} & \frac{1}{11} & - \frac{5}{11} & 1 & 0 & 0 \\ \frac{1}{11} & \frac{1}{11} & \frac{1}{22} & 0 & 1 & 0 \\ \frac{1}{11} & - \frac{10}{11} & \frac{1}{22} & 0 & 0 & 1 \end{array}]$

Step 4

Find the reduced row echelon form.

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Step 4.1

Multiply each element of $R_{1}$ by $11$ to make the entry at $1, 1$ a $1$ .

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Step 4.1.1

Multiply each element of $R_{1}$ by $11$ to make the entry at $1, 1$ a $1$ .

$[\begin{array}{c} 11 (\frac{1}{11}) & 11 (\frac{1}{11}) & 11 (- \frac{5}{11}) & 11 \cdot 1 & 11 \cdot 0 & 11 \cdot 0 \\ \frac{1}{11} & \frac{1}{11} & \frac{1}{22} & 0 & 1 & 0 \\ \frac{1}{11} & - \frac{10}{11} & \frac{1}{22} & 0 & 0 & 1 \end{array}]$

Step 4.1.2

Simplify $R_{1}$ .

$[\begin{array}{c} 1 & 1 & - 5 & 11 & 0 & 0 \\ \frac{1}{11} & \frac{1}{11} & \frac{1}{22} & 0 & 1 & 0 \\ \frac{1}{11} & - \frac{10}{11} & \frac{1}{22} & 0 & 0 & 1 \end{array}]$

Step 4.2

Perform the row operation $R_{2} = R_{2} - \frac{1}{11} R_{1}$ to make the entry at $2, 1$ a $0$ .

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Step 4.2.1

Perform the row operation $R_{2} = R_{2} - \frac{1}{11} R_{1}$ to make the entry at $2, 1$ a $0$ .

$[\begin{array}{c} 1 & 1 & - 5 & 11 & 0 & 0 \\ \frac{1}{11} - \frac{1}{11} \cdot 1 & \frac{1}{11} - \frac{1}{11} \cdot 1 & \frac{1}{22} - \frac{1}{11} \cdot - 5 & 0 - \frac{1}{11} \cdot 11 & 1 - \frac{1}{11} \cdot 0 & 0 - \frac{1}{11} \cdot 0 \\ \frac{1}{11} & - \frac{10}{11} & \frac{1}{22} & 0 & 0 & 1 \end{array}]$

Step 4.2.2

Simplify $R_{2}$ .

$[\begin{array}{c} 1 & 1 & - 5 & 11 & 0 & 0 \\ 0 & 0 & \frac{1}{2} & - 1 & 1 & 0 \\ \frac{1}{11} & - \frac{10}{11} & \frac{1}{22} & 0 & 0 & 1 \end{array}]$

Step 4.3

Perform the row operation $R_{3} = R_{3} - \frac{1}{11} R_{1}$ to make the entry at $3, 1$ a $0$ .

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Step 4.3.1

Perform the row operation $R_{3} = R_{3} - \frac{1}{11} R_{1}$ to make the entry at $3, 1$ a $0$ .

$[\begin{array}{c} 1 & 1 & - 5 & 11 & 0 & 0 \\ 0 & 0 & \frac{1}{2} & - 1 & 1 & 0 \\ \frac{1}{11} - \frac{1}{11} \cdot 1 & - \frac{10}{11} - \frac{1}{11} \cdot 1 & \frac{1}{22} - \frac{1}{11} \cdot - 5 & 0 - \frac{1}{11} \cdot 11 & 0 - \frac{1}{11} \cdot 0 & 1 - \frac{1}{11} \cdot 0 \end{array}]$

Step 4.3.2

Simplify $R_{3}$ .

$[\begin{array}{c} 1 & 1 & - 5 & 11 & 0 & 0 \\ 0 & 0 & \frac{1}{2} & - 1 & 1 & 0 \\ 0 & - 1 & \frac{1}{2} & - 1 & 0 & 1 \end{array}]$

Step 4.4

Swap $R_{3}$ with $R_{2}$ to put a nonzero entry at $2, 2$ .

$[\begin{array}{c} 1 & 1 & - 5 & 11 & 0 & 0 \\ 0 & - 1 & \frac{1}{2} & - 1 & 0 & 1 \\ 0 & 0 & \frac{1}{2} & - 1 & 1 & 0 \end{array}]$

Step 4.5

Multiply each element of $R_{2}$ by $- 1$ to make the entry at $2, 2$ a $1$ .

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Step 4.5.1

Multiply each element of $R_{2}$ by $- 1$ to make the entry at $2, 2$ a $1$ .

$[\begin{array}{c} 1 & 1 & - 5 & 11 & 0 & 0 \\ - 0 & - - 1 & - \frac{1}{2} & - - 1 & - 0 & - 1 \cdot 1 \\ 0 & 0 & \frac{1}{2} & - 1 & 1 & 0 \end{array}]$

Step 4.5.2

Simplify $R_{2}$ .

$[\begin{array}{c} 1 & 1 & - 5 & 11 & 0 & 0 \\ 0 & 1 & - \frac{1}{2} & 1 & 0 & - 1 \\ 0 & 0 & \frac{1}{2} & - 1 & 1 & 0 \end{array}]$

Step 4.6

Multiply each element of $R_{3}$ by $2$ to make the entry at $3, 3$ a $1$ .

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Step 4.6.1

Multiply each element of $R_{3}$ by $2$ to make the entry at $3, 3$ a $1$ .

$[\begin{array}{c} 1 & 1 & - 5 & 11 & 0 & 0 \\ 0 & 1 & - \frac{1}{2} & 1 & 0 & - 1 \\ 2 \cdot 0 & 2 \cdot 0 & 2 (\frac{1}{2}) & 2 \cdot - 1 & 2 \cdot 1 & 2 \cdot 0 \end{array}]$

Step 4.6.2

Simplify $R_{3}$ .

$[\begin{array}{c} 1 & 1 & - 5 & 11 & 0 & 0 \\ 0 & 1 & - \frac{1}{2} & 1 & 0 & - 1 \\ 0 & 0 & 1 & - 2 & 2 & 0 \end{array}]$

Step 4.7

Perform the row operation $R_{2} = R_{2} + \frac{1}{2} R_{3}$ to make the entry at $2, 3$ a $0$ .

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Step 4.7.1

Perform the row operation $R_{2} = R_{2} + \frac{1}{2} R_{3}$ to make the entry at $2, 3$ a $0$ .

$[\begin{array}{c} 1 & 1 & - 5 & 11 & 0 & 0 \\ 0 + \frac{1}{2} \cdot 0 & 1 + \frac{1}{2} \cdot 0 & - \frac{1}{2} + \frac{1}{2} \cdot 1 & 1 + \frac{1}{2} \cdot - 2 & 0 + \frac{1}{2} \cdot 2 & - 1 + \frac{1}{2} \cdot 0 \\ 0 & 0 & 1 & - 2 & 2 & 0 \end{array}]$

Step 4.7.2

Simplify $R_{2}$ .

$[\begin{array}{c} 1 & 1 & - 5 & 11 & 0 & 0 \\ 0 & 1 & 0 & 0 & 1 & - 1 \\ 0 & 0 & 1 & - 2 & 2 & 0 \end{array}]$

Step 4.8

Perform the row operation $R_{1} = R_{1} + 5 R_{3}$ to make the entry at $1, 3$ a $0$ .

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Step 4.8.1

Perform the row operation $R_{1} = R_{1} + 5 R_{3}$ to make the entry at $1, 3$ a $0$ .

$[\begin{array}{c} 1 + 5 \cdot 0 & 1 + 5 \cdot 0 & - 5 + 5 \cdot 1 & 11 + 5 \cdot - 2 & 0 + 5 \cdot 2 & 0 + 5 \cdot 0 \\ 0 & 1 & 0 & 0 & 1 & - 1 \\ 0 & 0 & 1 & - 2 & 2 & 0 \end{array}]$

Step 4.8.2

Simplify $R_{1}$ .

$[\begin{array}{c} 1 & 1 & 0 & 1 & 10 & 0 \\ 0 & 1 & 0 & 0 & 1 & - 1 \\ 0 & 0 & 1 & - 2 & 2 & 0 \end{array}]$

Step 4.9

Perform the row operation $R_{1} = R_{1} - R_{2}$ to make the entry at $1, 2$ a $0$ .

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Step 4.9.1

Perform the row operation $R_{1} = R_{1} - R_{2}$ to make the entry at $1, 2$ a $0$ .

$[\begin{array}{c} 1 - 0 & 1 - 1 & 0 - 0 & 1 - 0 & 10 - 1 & 0 + 1 \\ 0 & 1 & 0 & 0 & 1 & - 1 \\ 0 & 0 & 1 & - 2 & 2 & 0 \end{array}]$

Step 4.9.2

Simplify $R_{1}$ .

$[\begin{array}{c} 1 & 0 & 0 & 1 & 9 & 1 \\ 0 & 1 & 0 & 0 & 1 & - 1 \\ 0 & 0 & 1 & - 2 & 2 & 0 \end{array}]$

Step 5

The right half of the reduced row echelon form is the inverse.

$[\begin{array}{c} 1 & 9 & 1 \\ 0 & 1 & - 1 \\ - 2 & 2 & 0 \end{array}]$