Linear Algebra Examples

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

Step 1

Set up the formula to find the characteristic equation $p (λ)$ .

$p (λ) = determinant (A - λ I_{3})$

Step 2

The identity matrix or unit matrix of size $3$ is the $3 \times 3$ square matrix with ones on the main diagonal and zeros elsewhere.

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

Step 3

Substitute the known values into $p (λ) = determinant (A - λ I_{3})$ .

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Step 3.1

Substitute $[\begin{array}{c} 1 & - 1 & - 2 \\ 1 & 3 & 2 \\ 1 & - 1 & 2 \end{array}]$ for $A$ .

$p (λ) = determinant ([\begin{array}{c} 1 & - 1 & - 2 \\ 1 & 3 & 2 \\ 1 & - 1 & 2 \end{array}] - λ I_{3})$

Step 3.2

Substitute $[\begin{array}{c} 1 & 0 & 0 \\ 0 & 1 & 0 \\ 0 & 0 & 1 \end{array}]$ for $I_{3}$ .

$p (λ) = determinant ([\begin{array}{c} 1 & - 1 & - 2 \\ 1 & 3 & 2 \\ 1 & - 1 & 2 \end{array}] - λ [\begin{array}{c} 1 & 0 & 0 \\ 0 & 1 & 0 \\ 0 & 0 & 1 \end{array}])$

Step 4

Simplify.

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Step 4.1

Simplify each term.

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Step 4.1.1

Multiply $- λ$ by each element of the matrix.

$p (λ) = determinant ([\begin{array}{c} 1 & - 1 & - 2 \\ 1 & 3 & 2 \\ 1 & - 1 & 2 \end{array}] + [\begin{array}{c} - λ \cdot 1 & - λ \cdot 0 & - λ \cdot 0 \\ - λ \cdot 0 & - λ \cdot 1 & - λ \cdot 0 \\ - λ \cdot 0 & - λ \cdot 0 & - λ \cdot 1 \end{array}])$

Step 4.1.2

Simplify each element in the matrix.

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Step 4.1.2.1

Multiply $- 1$ by $1$ .

$p (λ) = determinant ([\begin{array}{c} 1 & - 1 & - 2 \\ 1 & 3 & 2 \\ 1 & - 1 & 2 \end{array}] + [\begin{array}{c} - λ & - λ \cdot 0 & - λ \cdot 0 \\ - λ \cdot 0 & - λ \cdot 1 & - λ \cdot 0 \\ - λ \cdot 0 & - λ \cdot 0 & - λ \cdot 1 \end{array}])$

Step 4.1.2.2

Multiply $- λ \cdot 0$ .

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Step 4.1.2.2.1

Multiply $0$ by $- 1$ .

$p (λ) = determinant ([\begin{array}{c} 1 & - 1 & - 2 \\ 1 & 3 & 2 \\ 1 & - 1 & 2 \end{array}] + [\begin{array}{c} - λ & 0 λ & - λ \cdot 0 \\ - λ \cdot 0 & - λ \cdot 1 & - λ \cdot 0 \\ - λ \cdot 0 & - λ \cdot 0 & - λ \cdot 1 \end{array}])$

Step 4.1.2.2.2

Multiply $0$ by $λ$ .

$p (λ) = determinant ([\begin{array}{c} 1 & - 1 & - 2 \\ 1 & 3 & 2 \\ 1 & - 1 & 2 \end{array}] + [\begin{array}{c} - λ & 0 & - λ \cdot 0 \\ - λ \cdot 0 & - λ \cdot 1 & - λ \cdot 0 \\ - λ \cdot 0 & - λ \cdot 0 & - λ \cdot 1 \end{array}])$

Step 4.1.2.3

Multiply $- λ \cdot 0$ .

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Step 4.1.2.3.1

Multiply $0$ by $- 1$ .

$p (λ) = determinant ([\begin{array}{c} 1 & - 1 & - 2 \\ 1 & 3 & 2 \\ 1 & - 1 & 2 \end{array}] + [\begin{array}{c} - λ & 0 & 0 λ \\ - λ \cdot 0 & - λ \cdot 1 & - λ \cdot 0 \\ - λ \cdot 0 & - λ \cdot 0 & - λ \cdot 1 \end{array}])$

Step 4.1.2.3.2

Multiply $0$ by $λ$ .

$p (λ) = determinant ([\begin{array}{c} 1 & - 1 & - 2 \\ 1 & 3 & 2 \\ 1 & - 1 & 2 \end{array}] + [\begin{array}{c} - λ & 0 & 0 \\ - λ \cdot 0 & - λ \cdot 1 & - λ \cdot 0 \\ - λ \cdot 0 & - λ \cdot 0 & - λ \cdot 1 \end{array}])$

Step 4.1.2.4

Multiply $- λ \cdot 0$ .

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Step 4.1.2.4.1

Multiply $0$ by $- 1$ .

$p (λ) = determinant ([\begin{array}{c} 1 & - 1 & - 2 \\ 1 & 3 & 2 \\ 1 & - 1 & 2 \end{array}] + [\begin{array}{c} - λ & 0 & 0 \\ 0 λ & - λ \cdot 1 & - λ \cdot 0 \\ - λ \cdot 0 & - λ \cdot 0 & - λ \cdot 1 \end{array}])$

Step 4.1.2.4.2

Multiply $0$ by $λ$ .

$p (λ) = determinant ([\begin{array}{c} 1 & - 1 & - 2 \\ 1 & 3 & 2 \\ 1 & - 1 & 2 \end{array}] + [\begin{array}{c} - λ & 0 & 0 \\ 0 & - λ \cdot 1 & - λ \cdot 0 \\ - λ \cdot 0 & - λ \cdot 0 & - λ \cdot 1 \end{array}])$

Step 4.1.2.5

Multiply $- 1$ by $1$ .

$p (λ) = determinant ([\begin{array}{c} 1 & - 1 & - 2 \\ 1 & 3 & 2 \\ 1 & - 1 & 2 \end{array}] + [\begin{array}{c} - λ & 0 & 0 \\ 0 & - λ & - λ \cdot 0 \\ - λ \cdot 0 & - λ \cdot 0 & - λ \cdot 1 \end{array}])$

Step 4.1.2.6

Multiply $- λ \cdot 0$ .

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Step 4.1.2.6.1

Multiply $0$ by $- 1$ .

$p (λ) = determinant ([\begin{array}{c} 1 & - 1 & - 2 \\ 1 & 3 & 2 \\ 1 & - 1 & 2 \end{array}] + [\begin{array}{c} - λ & 0 & 0 \\ 0 & - λ & 0 λ \\ - λ \cdot 0 & - λ \cdot 0 & - λ \cdot 1 \end{array}])$

Step 4.1.2.6.2

Multiply $0$ by $λ$ .

$p (λ) = determinant ([\begin{array}{c} 1 & - 1 & - 2 \\ 1 & 3 & 2 \\ 1 & - 1 & 2 \end{array}] + [\begin{array}{c} - λ & 0 & 0 \\ 0 & - λ & 0 \\ - λ \cdot 0 & - λ \cdot 0 & - λ \cdot 1 \end{array}])$

Step 4.1.2.7

Multiply $- λ \cdot 0$ .

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Step 4.1.2.7.1

Multiply $0$ by $- 1$ .

$p (λ) = determinant ([\begin{array}{c} 1 & - 1 & - 2 \\ 1 & 3 & 2 \\ 1 & - 1 & 2 \end{array}] + [\begin{array}{c} - λ & 0 & 0 \\ 0 & - λ & 0 \\ 0 λ & - λ \cdot 0 & - λ \cdot 1 \end{array}])$

Step 4.1.2.7.2

Multiply $0$ by $λ$ .

$p (λ) = determinant ([\begin{array}{c} 1 & - 1 & - 2 \\ 1 & 3 & 2 \\ 1 & - 1 & 2 \end{array}] + [\begin{array}{c} - λ & 0 & 0 \\ 0 & - λ & 0 \\ 0 & - λ \cdot 0 & - λ \cdot 1 \end{array}])$

Step 4.1.2.8

Multiply $- λ \cdot 0$ .

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Step 4.1.2.8.1

Multiply $0$ by $- 1$ .

$p (λ) = determinant ([\begin{array}{c} 1 & - 1 & - 2 \\ 1 & 3 & 2 \\ 1 & - 1 & 2 \end{array}] + [\begin{array}{c} - λ & 0 & 0 \\ 0 & - λ & 0 \\ 0 & 0 λ & - λ \cdot 1 \end{array}])$

Step 4.1.2.8.2

Multiply $0$ by $λ$ .

$p (λ) = determinant ([\begin{array}{c} 1 & - 1 & - 2 \\ 1 & 3 & 2 \\ 1 & - 1 & 2 \end{array}] + [\begin{array}{c} - λ & 0 & 0 \\ 0 & - λ & 0 \\ 0 & 0 & - λ \cdot 1 \end{array}])$

Step 4.1.2.9

Multiply $- 1$ by $1$ .

$p (λ) = determinant ([\begin{array}{c} 1 & - 1 & - 2 \\ 1 & 3 & 2 \\ 1 & - 1 & 2 \end{array}] + [\begin{array}{c} - λ & 0 & 0 \\ 0 & - λ & 0 \\ 0 & 0 & - λ \end{array}])$

Step 4.2

Add the corresponding elements.

$p (λ) = determinant [\begin{array}{c} 1 - λ & - 1 + 0 & - 2 + 0 \\ 1 + 0 & 3 - λ & 2 + 0 \\ 1 + 0 & - 1 + 0 & 2 - λ \end{array}]$

Step 4.3

Simplify each element.

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Step 4.3.1

Add $- 1$ and $0$ .

$p (λ) = determinant [\begin{array}{c} 1 - λ & - 1 & - 2 + 0 \\ 1 + 0 & 3 - λ & 2 + 0 \\ 1 + 0 & - 1 + 0 & 2 - λ \end{array}]$

Step 4.3.2

Add $- 2$ and $0$ .

$p (λ) = determinant [\begin{array}{c} 1 - λ & - 1 & - 2 \\ 1 + 0 & 3 - λ & 2 + 0 \\ 1 + 0 & - 1 + 0 & 2 - λ \end{array}]$

Step 4.3.3

Add $1$ and $0$ .

$p (λ) = determinant [\begin{array}{c} 1 - λ & - 1 & - 2 \\ 1 & 3 - λ & 2 + 0 \\ 1 + 0 & - 1 + 0 & 2 - λ \end{array}]$

Step 4.3.4

Add $2$ and $0$ .

$p (λ) = determinant [\begin{array}{c} 1 - λ & - 1 & - 2 \\ 1 & 3 - λ & 2 \\ 1 + 0 & - 1 + 0 & 2 - λ \end{array}]$

Step 4.3.5

Add $1$ and $0$ .

$p (λ) = determinant [\begin{array}{c} 1 - λ & - 1 & - 2 \\ 1 & 3 - λ & 2 \\ 1 & - 1 + 0 & 2 - λ \end{array}]$

Step 4.3.6

Add $- 1$ and $0$ .

$p (λ) = determinant [\begin{array}{c} 1 - λ & - 1 & - 2 \\ 1 & 3 - λ & 2 \\ 1 & - 1 & 2 - λ \end{array}]$

Step 5

Find the determinant.

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Step 5.1

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 5.1.1

Consider the corresponding sign chart.

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

Step 5.1.2

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

Step 5.1.3

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

$| \begin{array}{c} 3 - λ & 2 \\ - 1 & 2 - λ \end{array} |$

Step 5.1.4

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

$(1 - λ) | \begin{array}{c} 3 - λ & 2 \\ - 1 & 2 - λ \end{array} |$

Step 5.1.5

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

$| \begin{array}{c} 1 & 2 \\ 1 & 2 - λ \end{array} |$

Step 5.1.6

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

$1 | \begin{array}{c} 1 & 2 \\ 1 & 2 - λ \end{array} |$

Step 5.1.7

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

$| \begin{array}{c} 1 & 3 - λ \\ 1 & - 1 \end{array} |$

Step 5.1.8

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

$- 2 | \begin{array}{c} 1 & 3 - λ \\ 1 & - 1 \end{array} |$

Step 5.1.9

Add the terms together.

$p (λ) = (1 - λ) | \begin{array}{c} 3 - λ & 2 \\ - 1 & 2 - λ \end{array} | + 1 | \begin{array}{c} 1 & 2 \\ 1 & 2 - λ \end{array} | - 2 | \begin{array}{c} 1 & 3 - λ \\ 1 & - 1 \end{array} |$

Step 5.2

Evaluate $| \begin{array}{c} 3 - λ & 2 \\ - 1 & 2 - λ \end{array} |$ .

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Step 5.2.1

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

$p (λ) = (1 - λ) ((3 - λ) (2 - λ) - (- 1 \cdot 2)) + 1 | \begin{array}{c} 1 & 2 \\ 1 & 2 - λ \end{array} | - 2 | \begin{array}{c} 1 & 3 - λ \\ 1 & - 1 \end{array} |$

Step 5.2.2

Simplify the determinant.

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Step 5.2.2.1

Simplify each term.

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Step 5.2.2.1.1

Expand $(3 - λ) (2 - λ)$ using the FOIL Method.

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Step 5.2.2.1.1.1

Apply the distributive property.

$p (λ) = (1 - λ) (3 (2 - λ) - λ (2 - λ) - (- 1 \cdot 2)) + 1 | \begin{array}{c} 1 & 2 \\ 1 & 2 - λ \end{array} | - 2 | \begin{array}{c} 1 & 3 - λ \\ 1 & - 1 \end{array} |$

Step 5.2.2.1.1.2

Apply the distributive property.

$p (λ) = (1 - λ) (3 \cdot 2 + 3 (- λ) - λ (2 - λ) - (- 1 \cdot 2)) + 1 | \begin{array}{c} 1 & 2 \\ 1 & 2 - λ \end{array} | - 2 | \begin{array}{c} 1 & 3 - λ \\ 1 & - 1 \end{array} |$

Step 5.2.2.1.1.3

Apply the distributive property.

$p (λ) = (1 - λ) (3 \cdot 2 + 3 (- λ) - λ \cdot 2 - λ (- λ) - (- 1 \cdot 2)) + 1 | \begin{array}{c} 1 & 2 \\ 1 & 2 - λ \end{array} | - 2 | \begin{array}{c} 1 & 3 - λ \\ 1 & - 1 \end{array} |$

Step 5.2.2.1.2

Simplify and combine like terms.

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Step 5.2.2.1.2.1

Simplify each term.

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Step 5.2.2.1.2.1.1

Multiply $3$ by $2$ .

$p (λ) = (1 - λ) (6 + 3 (- λ) - λ \cdot 2 - λ (- λ) - (- 1 \cdot 2)) + 1 | \begin{array}{c} 1 & 2 \\ 1 & 2 - λ \end{array} | - 2 | \begin{array}{c} 1 & 3 - λ \\ 1 & - 1 \end{array} |$

Step 5.2.2.1.2.1.2

Multiply $- 1$ by $3$ .

$p (λ) = (1 - λ) (6 - 3 λ - λ \cdot 2 - λ (- λ) - (- 1 \cdot 2)) + 1 | \begin{array}{c} 1 & 2 \\ 1 & 2 - λ \end{array} | - 2 | \begin{array}{c} 1 & 3 - λ \\ 1 & - 1 \end{array} |$

Step 5.2.2.1.2.1.3

Multiply $2$ by $- 1$ .

$p (λ) = (1 - λ) (6 - 3 λ - 2 λ - λ (- λ) - (- 1 \cdot 2)) + 1 | \begin{array}{c} 1 & 2 \\ 1 & 2 - λ \end{array} | - 2 | \begin{array}{c} 1 & 3 - λ \\ 1 & - 1 \end{array} |$

Step 5.2.2.1.2.1.4

Rewrite using the commutative property of multiplication.

$p (λ) = (1 - λ) (6 - 3 λ - 2 λ - 1 \cdot - 1 λ \cdot λ - (- 1 \cdot 2)) + 1 | \begin{array}{c} 1 & 2 \\ 1 & 2 - λ \end{array} | - 2 | \begin{array}{c} 1 & 3 - λ \\ 1 & - 1 \end{array} |$

Step 5.2.2.1.2.1.5

Multiply $λ$ by $λ$ by adding the exponents.

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Step 5.2.2.1.2.1.5.1

Move $λ$ .

$p (λ) = (1 - λ) (6 - 3 λ - 2 λ - 1 \cdot - 1 (λ \cdot λ) - (- 1 \cdot 2)) + 1 | \begin{array}{c} 1 & 2 \\ 1 & 2 - λ \end{array} | - 2 | \begin{array}{c} 1 & 3 - λ \\ 1 & - 1 \end{array} |$

Step 5.2.2.1.2.1.5.2

Multiply $λ$ by $λ$ .

$p (λ) = (1 - λ) (6 - 3 λ - 2 λ - 1 \cdot - 1 λ^{2} - (- 1 \cdot 2)) + 1 | \begin{array}{c} 1 & 2 \\ 1 & 2 - λ \end{array} | - 2 | \begin{array}{c} 1 & 3 - λ \\ 1 & - 1 \end{array} |$

Step 5.2.2.1.2.1.6

Multiply $- 1$ by $- 1$ .

$p (λ) = (1 - λ) (6 - 3 λ - 2 λ + 1 λ^{2} - (- 1 \cdot 2)) + 1 | \begin{array}{c} 1 & 2 \\ 1 & 2 - λ \end{array} | - 2 | \begin{array}{c} 1 & 3 - λ \\ 1 & - 1 \end{array} |$

Step 5.2.2.1.2.1.7

Multiply $λ^{2}$ by $1$ .

$p (λ) = (1 - λ) (6 - 3 λ - 2 λ + λ^{2} - (- 1 \cdot 2)) + 1 | \begin{array}{c} 1 & 2 \\ 1 & 2 - λ \end{array} | - 2 | \begin{array}{c} 1 & 3 - λ \\ 1 & - 1 \end{array} |$

Step 5.2.2.1.2.2

Subtract $2 λ$ from $- 3 λ$ .

$p (λ) = (1 - λ) (6 - 5 λ + λ^{2} - (- 1 \cdot 2)) + 1 | \begin{array}{c} 1 & 2 \\ 1 & 2 - λ \end{array} | - 2 | \begin{array}{c} 1 & 3 - λ \\ 1 & - 1 \end{array} |$

Step 5.2.2.1.3

Multiply $- (- 1 \cdot 2)$ .

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Step 5.2.2.1.3.1

Multiply $- 1$ by $2$ .

$p (λ) = (1 - λ) (6 - 5 λ + λ^{2} - - 2) + 1 | \begin{array}{c} 1 & 2 \\ 1 & 2 - λ \end{array} | - 2 | \begin{array}{c} 1 & 3 - λ \\ 1 & - 1 \end{array} |$

Step 5.2.2.1.3.2

Multiply $- 1$ by $- 2$ .

$p (λ) = (1 - λ) (6 - 5 λ + λ^{2} + 2) + 1 | \begin{array}{c} 1 & 2 \\ 1 & 2 - λ \end{array} | - 2 | \begin{array}{c} 1 & 3 - λ \\ 1 & - 1 \end{array} |$

Step 5.2.2.2

Add $6$ and $2$ .

$p (λ) = (1 - λ) (- 5 λ + λ^{2} + 8) + 1 | \begin{array}{c} 1 & 2 \\ 1 & 2 - λ \end{array} | - 2 | \begin{array}{c} 1 & 3 - λ \\ 1 & - 1 \end{array} |$

Step 5.2.2.3

Reorder $- 5 λ$ and $λ^{2}$ .

$p (λ) = (1 - λ) (λ^{2} - 5 λ + 8) + 1 | \begin{array}{c} 1 & 2 \\ 1 & 2 - λ \end{array} | - 2 | \begin{array}{c} 1 & 3 - λ \\ 1 & - 1 \end{array} |$

Step 5.3

Evaluate $| \begin{array}{c} 1 & 2 \\ 1 & 2 - λ \end{array} |$ .

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Step 5.3.1

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

$p (λ) = (1 - λ) (λ^{2} - 5 λ + 8) + 1 (1 (2 - λ) - 1 \cdot 2) - 2 | \begin{array}{c} 1 & 3 - λ \\ 1 & - 1 \end{array} |$

Step 5.3.2

Simplify the determinant.

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Step 5.3.2.1

Simplify each term.

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Step 5.3.2.1.1

Multiply $2 - λ$ by $1$ .

$p (λ) = (1 - λ) (λ^{2} - 5 λ + 8) + 1 (2 - λ - 1 \cdot 2) - 2 | \begin{array}{c} 1 & 3 - λ \\ 1 & - 1 \end{array} |$

Step 5.3.2.1.2

Multiply $- 1$ by $2$ .

$p (λ) = (1 - λ) (λ^{2} - 5 λ + 8) + 1 (2 - λ - 2) - 2 | \begin{array}{c} 1 & 3 - λ \\ 1 & - 1 \end{array} |$

Step 5.3.2.2

Combine the opposite terms in $2 - λ - 2$ .

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Step 5.3.2.2.1

Subtract $2$ from $2$ .

$p (λ) = (1 - λ) (λ^{2} - 5 λ + 8) + 1 (- λ + 0) - 2 | \begin{array}{c} 1 & 3 - λ \\ 1 & - 1 \end{array} |$

Step 5.3.2.2.2

Add $- λ$ and $0$ .

$p (λ) = (1 - λ) (λ^{2} - 5 λ + 8) + 1 (- λ) - 2 | \begin{array}{c} 1 & 3 - λ \\ 1 & - 1 \end{array} |$

Step 5.4

Evaluate $| \begin{array}{c} 1 & 3 - λ \\ 1 & - 1 \end{array} |$ .

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Step 5.4.1

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

$p (λ) = (1 - λ) (λ^{2} - 5 λ + 8) + 1 (- λ) - 2 (1 \cdot - 1 - (3 - λ))$

Step 5.4.2

Simplify the determinant.

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Step 5.4.2.1

Simplify each term.

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Step 5.4.2.1.1

Multiply $- 1$ by $1$ .

$p (λ) = (1 - λ) (λ^{2} - 5 λ + 8) + 1 (- λ) - 2 (- 1 - (3 - λ))$

Step 5.4.2.1.2

Apply the distributive property.

$p (λ) = (1 - λ) (λ^{2} - 5 λ + 8) + 1 (- λ) - 2 (- 1 - 1 \cdot 3 - - λ)$

Step 5.4.2.1.3

Multiply $- 1$ by $3$ .

$p (λ) = (1 - λ) (λ^{2} - 5 λ + 8) + 1 (- λ) - 2 (- 1 - 3 - - λ)$

Step 5.4.2.1.4

Multiply $- - λ$ .

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Step 5.4.2.1.4.1

Multiply $- 1$ by $- 1$ .

$p (λ) = (1 - λ) (λ^{2} - 5 λ + 8) + 1 (- λ) - 2 (- 1 - 3 + 1 λ)$

Step 5.4.2.1.4.2

Multiply $λ$ by $1$ .

$p (λ) = (1 - λ) (λ^{2} - 5 λ + 8) + 1 (- λ) - 2 (- 1 - 3 + λ)$

Step 5.4.2.2

Subtract $3$ from $- 1$ .

$p (λ) = (1 - λ) (λ^{2} - 5 λ + 8) + 1 (- λ) - 2 (- 4 + λ)$

Step 5.4.2.3

Reorder $- 4$ and $λ$ .

$p (λ) = (1 - λ) (λ^{2} - 5 λ + 8) + 1 (- λ) - 2 (λ - 4)$

Step 5.5

Simplify the determinant.

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Step 5.5.1

Simplify each term.

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Step 5.5.1.1

Expand $(1 - λ) (λ^{2} - 5 λ + 8)$ by multiplying each term in the first expression by each term in the second expression.

$p (λ) = 1 λ^{2} + 1 (- 5 λ) + 1 \cdot 8 - λ \cdot λ^{2} - λ (- 5 λ) - λ \cdot 8 + 1 (- λ) - 2 (λ - 4)$

Step 5.5.1.2

Simplify each term.

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Step 5.5.1.2.1

Multiply $λ^{2}$ by $1$ .

$p (λ) = λ^{2} + 1 (- 5 λ) + 1 \cdot 8 - λ \cdot λ^{2} - λ (- 5 λ) - λ \cdot 8 + 1 (- λ) - 2 (λ - 4)$

Step 5.5.1.2.2

Multiply $- 5 λ$ by $1$ .

$p (λ) = λ^{2} - 5 λ + 1 \cdot 8 - λ \cdot λ^{2} - λ (- 5 λ) - λ \cdot 8 + 1 (- λ) - 2 (λ - 4)$

Step 5.5.1.2.3

Multiply $8$ by $1$ .

$p (λ) = λ^{2} - 5 λ + 8 - λ \cdot λ^{2} - λ (- 5 λ) - λ \cdot 8 + 1 (- λ) - 2 (λ - 4)$

Step 5.5.1.2.4

Multiply $λ$ by $λ^{2}$ by adding the exponents.

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Step 5.5.1.2.4.1

Move $λ^{2}$ .

$p (λ) = λ^{2} - 5 λ + 8 - (λ^{2} λ) - λ (- 5 λ) - λ \cdot 8 + 1 (- λ) - 2 (λ - 4)$

Step 5.5.1.2.4.2

Multiply $λ^{2}$ by $λ$ .

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Step 5.5.1.2.4.2.1

Raise $λ$ to the power of $1$ .

$p (λ) = λ^{2} - 5 λ + 8 - (λ^{2} λ^{1}) - λ (- 5 λ) - λ \cdot 8 + 1 (- λ) - 2 (λ - 4)$

Step 5.5.1.2.4.2.2

Use the power rule $a^{m} a^{n} = a^{m + n}$ to combine exponents.

$p (λ) = λ^{2} - 5 λ + 8 - λ^{2 + 1} - λ (- 5 λ) - λ \cdot 8 + 1 (- λ) - 2 (λ - 4)$

Step 5.5.1.2.4.3

Add $2$ and $1$ .

$p (λ) = λ^{2} - 5 λ + 8 - λ^{3} - λ (- 5 λ) - λ \cdot 8 + 1 (- λ) - 2 (λ - 4)$

Step 5.5.1.2.5

Rewrite using the commutative property of multiplication.

$p (λ) = λ^{2} - 5 λ + 8 - λ^{3} - 1 \cdot - 5 λ \cdot λ - λ \cdot 8 + 1 (- λ) - 2 (λ - 4)$

Step 5.5.1.2.6

Multiply $λ$ by $λ$ by adding the exponents.

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Step 5.5.1.2.6.1

Move $λ$ .

$p (λ) = λ^{2} - 5 λ + 8 - λ^{3} - 1 \cdot - 5 (λ \cdot λ) - λ \cdot 8 + 1 (- λ) - 2 (λ - 4)$

Step 5.5.1.2.6.2

Multiply $λ$ by $λ$ .

$p (λ) = λ^{2} - 5 λ + 8 - λ^{3} - 1 \cdot - 5 λ^{2} - λ \cdot 8 + 1 (- λ) - 2 (λ - 4)$

Step 5.5.1.2.7

Multiply $- 1$ by $- 5$ .

$p (λ) = λ^{2} - 5 λ + 8 - λ^{3} + 5 λ^{2} - λ \cdot 8 + 1 (- λ) - 2 (λ - 4)$

Step 5.5.1.2.8

Multiply $8$ by $- 1$ .

$p (λ) = λ^{2} - 5 λ + 8 - λ^{3} + 5 λ^{2} - 8 λ + 1 (- λ) - 2 (λ - 4)$

Step 5.5.1.3

Add $λ^{2}$ and $5 λ^{2}$ .

$p (λ) = 6 λ^{2} - 5 λ + 8 - λ^{3} - 8 λ + 1 (- λ) - 2 (λ - 4)$

Step 5.5.1.4

Subtract $8 λ$ from $- 5 λ$ .

$p (λ) = 6 λ^{2} - 13 λ + 8 - λ^{3} + 1 (- λ) - 2 (λ - 4)$

Step 5.5.1.5

Multiply $- λ$ by $1$ .

$p (λ) = 6 λ^{2} - 13 λ + 8 - λ^{3} - λ - 2 (λ - 4)$

Step 5.5.1.6

Apply the distributive property.

$p (λ) = 6 λ^{2} - 13 λ + 8 - λ^{3} - λ - 2 λ - 2 \cdot - 4$

Step 5.5.1.7

Multiply $- 2$ by $- 4$ .

$p (λ) = 6 λ^{2} - 13 λ + 8 - λ^{3} - λ - 2 λ + 8$

Step 5.5.2

Subtract $λ$ from $- 13 λ$ .

$p (λ) = 6 λ^{2} - 14 λ + 8 - λ^{3} - 2 λ + 8$

Step 5.5.3

Subtract $2 λ$ from $- 14 λ$ .

$p (λ) = 6 λ^{2} - 16 λ + 8 - λ^{3} + 8$

Step 5.5.4

Add $8$ and $8$ .

$p (λ) = 6 λ^{2} - 16 λ - λ^{3} + 16$

Step 5.5.5

Move $- 16 λ$ .

$p (λ) = 6 λ^{2} - λ^{3} - 16 λ + 16$

Step 5.5.6

Reorder $6 λ^{2}$ and $- λ^{3}$ .

$p (λ) = - λ^{3} + 6 λ^{2} - 16 λ + 16$

Step 6

Set the characteristic polynomial equal to $0$ to find the eigenvalues $λ$ .

$- λ^{3} + 6 λ^{2} - 16 λ + 16 = 0$

Step 7

Solve for $λ$ .

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Step 7.1

Factor $- λ^{3} + 6 λ^{2} - 16 λ + 16$ using the rational roots test.

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Step 7.1.1

If a polynomial function has integer coefficients, then every rational zero will have the form $\frac{p}{q}$ where $p$ is a factor of the constant and $q$ is a factor of the leading coefficient.

$p = \pm 1, \pm 16, \pm 2, \pm 8, \pm 4$

$q = \pm 1$

Step 7.1.2

Find every combination of $\pm \frac{p}{q}$ . These are the possible roots of the polynomial function.

$\pm 1, \pm 16, \pm 2, \pm 8, \pm 4$

Step 7.1.3

Substitute $2$ and simplify the expression. In this case, the expression is equal to $0$ so $2$ is a root of the polynomial.

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Step 7.1.3.1

Substitute $2$ into the polynomial.

$- 2^{3} + 6 \cdot 2^{2} - 16 \cdot 2 + 16$

Step 7.1.3.2

Raise $2$ to the power of $3$ .

$- 1 \cdot 8 + 6 \cdot 2^{2} - 16 \cdot 2 + 16$

Step 7.1.3.3

Multiply $- 1$ by $8$ .

$- 8 + 6 \cdot 2^{2} - 16 \cdot 2 + 16$

Step 7.1.3.4

Raise $2$ to the power of $2$ .

$- 8 + 6 \cdot 4 - 16 \cdot 2 + 16$

Step 7.1.3.5

Multiply $6$ by $4$ .

$- 8 + 24 - 16 \cdot 2 + 16$

Step 7.1.3.6

Add $- 8$ and $24$ .

$16 - 16 \cdot 2 + 16$

Step 7.1.3.7

Multiply $- 16$ by $2$ .

$16 - 32 + 16$

Step 7.1.3.8

Subtract $32$ from $16$ .

$- 16 + 16$

Step 7.1.3.9

Add $- 16$ and $16$ .

$0$

Step 7.1.4

Since $2$ is a known root, divide the polynomial by $λ - 2$ to find the quotient polynomial. This polynomial can then be used to find the remaining roots.

$\frac{- λ^{3} + 6 λ^{2} - 16 λ + 16}{λ - 2}$

Step 7.1.5

Divide $- λ^{3} + 6 λ^{2} - 16 λ + 16$ by $λ - 2$ .

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Step 7.1.5.1

Set up the polynomials to be divided. If there is not a term for every exponent, insert one with a value of $0$ .

$λ$

$2$

$λ^{3}$

$6 λ^{2}$

$16 λ$

$16$

Step 7.1.5.2

Divide the highest order term in the dividend $- λ^{3}$ by the highest order term in divisor $λ$ .

				-	$λ^{2}$
	$λ$	-	$2$	-	$λ^{3}$	+	$6 λ^{2}$	-	$16 λ$	+	$16$

Step 7.1.5.3

Multiply the new quotient term by the divisor.

			-	$λ^{2}$
$λ$	-	$2$	-	$λ^{3}$	+	$6 λ^{2}$	-	$16 λ$	+	$16$
			-	$λ^{3}$	+	$2 λ^{2}$

Step 7.1.5.4

The expression needs to be subtracted from the dividend, so change all the signs in $- λ^{3} + 2 λ^{2}$

			-	$λ^{2}$
$λ$	-	$2$	-	$λ^{3}$	+	$6 λ^{2}$	-	$16 λ$	+	$16$
			+	$λ^{3}$	-	$2 λ^{2}$

Step 7.1.5.5

After changing the signs, add the last dividend from the multiplied polynomial to find the new dividend.

			-	$λ^{2}$
$λ$	-	$2$	-	$λ^{3}$	+	$6 λ^{2}$	-	$16 λ$	+	$16$
			+	$λ^{3}$	-	$2 λ^{2}$
					+	$4 λ^{2}$

Step 7.1.5.6

Pull the next terms from the original dividend down into the current dividend.

			-	$λ^{2}$
$λ$	-	$2$	-	$λ^{3}$	+	$6 λ^{2}$	-	$16 λ$	+	$16$
			+	$λ^{3}$	-	$2 λ^{2}$
					+	$4 λ^{2}$	-	$16 λ$

Step 7.1.5.7

Divide the highest order term in the dividend $4 λ^{2}$ by the highest order term in divisor $λ$ .

			-	$λ^{2}$	+	$4 λ$
$λ$	-	$2$	-	$λ^{3}$	+	$6 λ^{2}$	-	$16 λ$	+	$16$
			+	$λ^{3}$	-	$2 λ^{2}$
					+	$4 λ^{2}$	-	$16 λ$

Step 7.1.5.8

Multiply the new quotient term by the divisor.

			-	$λ^{2}$	+	$4 λ$
$λ$	-	$2$	-	$λ^{3}$	+	$6 λ^{2}$	-	$16 λ$	+	$16$
			+	$λ^{3}$	-	$2 λ^{2}$
					+	$4 λ^{2}$	-	$16 λ$
					+	$4 λ^{2}$	-	$8 λ$

Step 7.1.5.9

The expression needs to be subtracted from the dividend, so change all the signs in $4 λ^{2} - 8 λ$

			-	$λ^{2}$	+	$4 λ$
$λ$	-	$2$	-	$λ^{3}$	+	$6 λ^{2}$	-	$16 λ$	+	$16$
			+	$λ^{3}$	-	$2 λ^{2}$
					+	$4 λ^{2}$	-	$16 λ$
					-	$4 λ^{2}$	+	$8 λ$

Step 7.1.5.10

After changing the signs, add the last dividend from the multiplied polynomial to find the new dividend.

			-	$λ^{2}$	+	$4 λ$
$λ$	-	$2$	-	$λ^{3}$	+	$6 λ^{2}$	-	$16 λ$	+	$16$
			+	$λ^{3}$	-	$2 λ^{2}$
					+	$4 λ^{2}$	-	$16 λ$
					-	$4 λ^{2}$	+	$8 λ$
							-	$8 λ$

Step 7.1.5.11

Pull the next terms from the original dividend down into the current dividend.

			-	$λ^{2}$	+	$4 λ$
$λ$	-	$2$	-	$λ^{3}$	+	$6 λ^{2}$	-	$16 λ$	+	$16$
			+	$λ^{3}$	-	$2 λ^{2}$
					+	$4 λ^{2}$	-	$16 λ$
					-	$4 λ^{2}$	+	$8 λ$
							-	$8 λ$	+	$16$

Step 7.1.5.12

Divide the highest order term in the dividend $- 8 λ$ by the highest order term in divisor $λ$ .

			-	$λ^{2}$	+	$4 λ$	-	$8$
$λ$	-	$2$	-	$λ^{3}$	+	$6 λ^{2}$	-	$16 λ$	+	$16$
			+	$λ^{3}$	-	$2 λ^{2}$
					+	$4 λ^{2}$	-	$16 λ$
					-	$4 λ^{2}$	+	$8 λ$
							-	$8 λ$	+	$16$

Step 7.1.5.13

Multiply the new quotient term by the divisor.

			-	$λ^{2}$	+	$4 λ$	-	$8$
$λ$	-	$2$	-	$λ^{3}$	+	$6 λ^{2}$	-	$16 λ$	+	$16$
			+	$λ^{3}$	-	$2 λ^{2}$
					+	$4 λ^{2}$	-	$16 λ$
					-	$4 λ^{2}$	+	$8 λ$
							-	$8 λ$	+	$16$
							-	$8 λ$	+	$16$

Step 7.1.5.14

The expression needs to be subtracted from the dividend, so change all the signs in $- 8 λ + 16$

			-	$λ^{2}$	+	$4 λ$	-	$8$
$λ$	-	$2$	-	$λ^{3}$	+	$6 λ^{2}$	-	$16 λ$	+	$16$
			+	$λ^{3}$	-	$2 λ^{2}$
					+	$4 λ^{2}$	-	$16 λ$
					-	$4 λ^{2}$	+	$8 λ$
							-	$8 λ$	+	$16$
							+	$8 λ$	-	$16$

Step 7.1.5.15

After changing the signs, add the last dividend from the multiplied polynomial to find the new dividend.

			-	$λ^{2}$	+	$4 λ$	-	$8$
$λ$	-	$2$	-	$λ^{3}$	+	$6 λ^{2}$	-	$16 λ$	+	$16$
			+	$λ^{3}$	-	$2 λ^{2}$
					+	$4 λ^{2}$	-	$16 λ$
					-	$4 λ^{2}$	+	$8 λ$
							-	$8 λ$	+	$16$
							+	$8 λ$	-	$16$
										$0$

Step 7.1.5.16

Since the remander is $0$ , the final answer is the quotient.

$- λ^{2} + 4 λ - 8$

Step 7.1.6

Write $- λ^{3} + 6 λ^{2} - 16 λ + 16$ as a set of factors.

$(λ - 2) (- λ^{2} + 4 λ - 8) = 0$

Step 7.2

If any individual factor on the left side of the equation is equal to $0$ , the entire expression will be equal to $0$ .

$λ - 2 = 0$

$- λ^{2} + 4 λ - 8 = 0$

Step 7.3

Set $λ - 2$ equal to $0$ and solve for $λ$ .

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Step 7.3.1

Set $λ - 2$ equal to $0$ .

$λ - 2 = 0$

Step 7.3.2

Add $2$ to both sides of the equation.

$λ = 2$

Step 7.4

Set $- λ^{2} + 4 λ - 8$ equal to $0$ and solve for $λ$ .

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Step 7.4.1

Set $- λ^{2} + 4 λ - 8$ equal to $0$ .

$- λ^{2} + 4 λ - 8 = 0$

Step 7.4.2

Solve $- λ^{2} + 4 λ - 8 = 0$ for $λ$ .

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Step 7.4.2.1

Use the quadratic formula to find the solutions.

$\frac{- b \pm \sqrt{b^{2} - 4 (a c)}}{2 a}$

Step 7.4.2.2

Substitute the values $a = - 1$ , $b = 4$ , and $c = - 8$ into the quadratic formula and solve for $λ$ .

$\frac{- 4 \pm \sqrt{4^{2} - 4 \cdot (- 1 \cdot - 8)}}{2 \cdot - 1}$

Step 7.4.2.3

Simplify.

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Step 7.4.2.3.1

Simplify the numerator.

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Step 7.4.2.3.1.1

Raise $4$ to the power of $2$ .

$λ = \frac{- 4 \pm \sqrt{16 - 4 \cdot - 1 \cdot - 8}}{2 \cdot - 1}$

Step 7.4.2.3.1.2

Multiply $- 4 \cdot - 1 \cdot - 8$ .

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Step 7.4.2.3.1.2.1

Multiply $- 4$ by $- 1$ .

$λ = \frac{- 4 \pm \sqrt{16 + 4 \cdot - 8}}{2 \cdot - 1}$

Step 7.4.2.3.1.2.2

Multiply $4$ by $- 8$ .

$λ = \frac{- 4 \pm \sqrt{16 - 32}}{2 \cdot - 1}$

Step 7.4.2.3.1.3

Subtract $32$ from $16$ .

$λ = \frac{- 4 \pm \sqrt{- 16}}{2 \cdot - 1}$

Step 7.4.2.3.1.4

Rewrite $- 16$ as $- 1 (16)$ .

$λ = \frac{- 4 \pm \sqrt{- 1 \cdot 16}}{2 \cdot - 1}$

Step 7.4.2.3.1.5

Rewrite $\sqrt{- 1 (16)}$ as $\sqrt{- 1} \cdot \sqrt{16}$ .

$λ = \frac{- 4 \pm \sqrt{- 1} \cdot \sqrt{16}}{2 \cdot - 1}$

Step 7.4.2.3.1.6

Rewrite $\sqrt{- 1}$ as $i$ .

$λ = \frac{- 4 \pm i \cdot \sqrt{16}}{2 \cdot - 1}$

Step 7.4.2.3.1.7

Rewrite $16$ as $4^{2}$ .

$λ = \frac{- 4 \pm i \cdot \sqrt{4^{2}}}{2 \cdot - 1}$

Step 7.4.2.3.1.8

Pull terms out from under the radical, assuming positive real numbers.

$λ = \frac{- 4 \pm i \cdot 4}{2 \cdot - 1}$

Step 7.4.2.3.1.9

Move $4$ to the left of $i$ .

$λ = \frac{- 4 \pm 4 i}{2 \cdot - 1}$

Step 7.4.2.3.2

Multiply $2$ by $- 1$ .

$λ = \frac{- 4 \pm 4 i}{- 2}$

Step 7.4.2.3.3

Simplify $\frac{- 4 \pm 4 i}{- 2}$ .

$λ = 2 \pm 2 i$

Step 7.4.2.4

The final answer is the combination of both solutions.

$λ = 2 + 2 i, 2 - 2 i$

Step 7.5

The final solution is all the values that make $(λ - 2) (- λ^{2} + 4 λ - 8) = 0$ true.

$λ = 2, 2 + 2 i, 2 - 2 i$