Linear Algebra Examples

$2 [\begin{array}{c} 1 & - 3 & 0 \\ 4 & 5 & 1 \\ 3 & 8 & 0 \end{array}] \cdot [\begin{array}{c} 1 & 1 & - 2 \\ 3 & 0 & 4 \\ - 1 & 3 & 2 \end{array}] + [\begin{array}{c} 2 & 0 & - 2 \\ 4 & 7 & - 5 \\ 1 & 0 & - 1 \end{array}] \cdot [\begin{array}{c} 2 & 0 & - 2 \\ 4 & 7 & - 5 \\ 1 & 0 & - 1 \end{array}]$

Step 1

Simplify each term.

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Step 1.1

Multiply $2$ by each element of the matrix.

$[\begin{array}{c} 2 \cdot 1 & 2 \cdot - 3 & 2 \cdot 0 \\ 2 \cdot 4 & 2 \cdot 5 & 2 \cdot 1 \\ 2 \cdot 3 & 2 \cdot 8 & 2 \cdot 0 \end{array}] \cdot [\begin{array}{c} 1 & 1 & - 2 \\ 3 & 0 & 4 \\ - 1 & 3 & 2 \end{array}] + [\begin{array}{c} 2 & 0 & - 2 \\ 4 & 7 & - 5 \\ 1 & 0 & - 1 \end{array}] \cdot [\begin{array}{c} 2 & 0 & - 2 \\ 4 & 7 & - 5 \\ 1 & 0 & - 1 \end{array}]$

Step 1.2

Simplify each element in the matrix.

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Step 1.2.1

Multiply $2$ by $1$ .

$[\begin{array}{c} 2 & 2 \cdot - 3 & 2 \cdot 0 \\ 2 \cdot 4 & 2 \cdot 5 & 2 \cdot 1 \\ 2 \cdot 3 & 2 \cdot 8 & 2 \cdot 0 \end{array}] \cdot [\begin{array}{c} 1 & 1 & - 2 \\ 3 & 0 & 4 \\ - 1 & 3 & 2 \end{array}] + [\begin{array}{c} 2 & 0 & - 2 \\ 4 & 7 & - 5 \\ 1 & 0 & - 1 \end{array}] \cdot [\begin{array}{c} 2 & 0 & - 2 \\ 4 & 7 & - 5 \\ 1 & 0 & - 1 \end{array}]$

Step 1.2.2

Multiply $2$ by $- 3$ .

$[\begin{array}{c} 2 & - 6 & 2 \cdot 0 \\ 2 \cdot 4 & 2 \cdot 5 & 2 \cdot 1 \\ 2 \cdot 3 & 2 \cdot 8 & 2 \cdot 0 \end{array}] \cdot [\begin{array}{c} 1 & 1 & - 2 \\ 3 & 0 & 4 \\ - 1 & 3 & 2 \end{array}] + [\begin{array}{c} 2 & 0 & - 2 \\ 4 & 7 & - 5 \\ 1 & 0 & - 1 \end{array}] \cdot [\begin{array}{c} 2 & 0 & - 2 \\ 4 & 7 & - 5 \\ 1 & 0 & - 1 \end{array}]$

Step 1.2.3

Multiply $2$ by $0$ .

$[\begin{array}{c} 2 & - 6 & 0 \\ 2 \cdot 4 & 2 \cdot 5 & 2 \cdot 1 \\ 2 \cdot 3 & 2 \cdot 8 & 2 \cdot 0 \end{array}] \cdot [\begin{array}{c} 1 & 1 & - 2 \\ 3 & 0 & 4 \\ - 1 & 3 & 2 \end{array}] + [\begin{array}{c} 2 & 0 & - 2 \\ 4 & 7 & - 5 \\ 1 & 0 & - 1 \end{array}] \cdot [\begin{array}{c} 2 & 0 & - 2 \\ 4 & 7 & - 5 \\ 1 & 0 & - 1 \end{array}]$

Step 1.2.4

Multiply $2$ by $4$ .

$[\begin{array}{c} 2 & - 6 & 0 \\ 8 & 2 \cdot 5 & 2 \cdot 1 \\ 2 \cdot 3 & 2 \cdot 8 & 2 \cdot 0 \end{array}] \cdot [\begin{array}{c} 1 & 1 & - 2 \\ 3 & 0 & 4 \\ - 1 & 3 & 2 \end{array}] + [\begin{array}{c} 2 & 0 & - 2 \\ 4 & 7 & - 5 \\ 1 & 0 & - 1 \end{array}] \cdot [\begin{array}{c} 2 & 0 & - 2 \\ 4 & 7 & - 5 \\ 1 & 0 & - 1 \end{array}]$

Step 1.2.5

Multiply $2$ by $5$ .

$[\begin{array}{c} 2 & - 6 & 0 \\ 8 & 10 & 2 \cdot 1 \\ 2 \cdot 3 & 2 \cdot 8 & 2 \cdot 0 \end{array}] \cdot [\begin{array}{c} 1 & 1 & - 2 \\ 3 & 0 & 4 \\ - 1 & 3 & 2 \end{array}] + [\begin{array}{c} 2 & 0 & - 2 \\ 4 & 7 & - 5 \\ 1 & 0 & - 1 \end{array}] \cdot [\begin{array}{c} 2 & 0 & - 2 \\ 4 & 7 & - 5 \\ 1 & 0 & - 1 \end{array}]$

Step 1.2.6

Multiply $2$ by $1$ .

$[\begin{array}{c} 2 & - 6 & 0 \\ 8 & 10 & 2 \\ 2 \cdot 3 & 2 \cdot 8 & 2 \cdot 0 \end{array}] \cdot [\begin{array}{c} 1 & 1 & - 2 \\ 3 & 0 & 4 \\ - 1 & 3 & 2 \end{array}] + [\begin{array}{c} 2 & 0 & - 2 \\ 4 & 7 & - 5 \\ 1 & 0 & - 1 \end{array}] \cdot [\begin{array}{c} 2 & 0 & - 2 \\ 4 & 7 & - 5 \\ 1 & 0 & - 1 \end{array}]$

Step 1.2.7

Multiply $2$ by $3$ .

$[\begin{array}{c} 2 & - 6 & 0 \\ 8 & 10 & 2 \\ 6 & 2 \cdot 8 & 2 \cdot 0 \end{array}] \cdot [\begin{array}{c} 1 & 1 & - 2 \\ 3 & 0 & 4 \\ - 1 & 3 & 2 \end{array}] + [\begin{array}{c} 2 & 0 & - 2 \\ 4 & 7 & - 5 \\ 1 & 0 & - 1 \end{array}] \cdot [\begin{array}{c} 2 & 0 & - 2 \\ 4 & 7 & - 5 \\ 1 & 0 & - 1 \end{array}]$

Step 1.2.8

Multiply $2$ by $8$ .

$[\begin{array}{c} 2 & - 6 & 0 \\ 8 & 10 & 2 \\ 6 & 16 & 2 \cdot 0 \end{array}] \cdot [\begin{array}{c} 1 & 1 & - 2 \\ 3 & 0 & 4 \\ - 1 & 3 & 2 \end{array}] + [\begin{array}{c} 2 & 0 & - 2 \\ 4 & 7 & - 5 \\ 1 & 0 & - 1 \end{array}] \cdot [\begin{array}{c} 2 & 0 & - 2 \\ 4 & 7 & - 5 \\ 1 & 0 & - 1 \end{array}]$

Step 1.2.9

Multiply $2$ by $0$ .

$[\begin{array}{c} 2 & - 6 & 0 \\ 8 & 10 & 2 \\ 6 & 16 & 0 \end{array}] \cdot [\begin{array}{c} 1 & 1 & - 2 \\ 3 & 0 & 4 \\ - 1 & 3 & 2 \end{array}] + [\begin{array}{c} 2 & 0 & - 2 \\ 4 & 7 & - 5 \\ 1 & 0 & - 1 \end{array}] \cdot [\begin{array}{c} 2 & 0 & - 2 \\ 4 & 7 & - 5 \\ 1 & 0 & - 1 \end{array}]$

Step 1.3

Multiply $[\begin{array}{c} 2 & - 6 & 0 \\ 8 & 10 & 2 \\ 6 & 16 & 0 \end{array}] [\begin{array}{c} 1 & 1 & - 2 \\ 3 & 0 & 4 \\ - 1 & 3 & 2 \end{array}]$ .

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Step 1.3.1

Two matrices can be multiplied if and only if the number of columns in the first matrix is equal to the number of rows in the second matrix. In this case, the first matrix is $3 \times 3$ and the second matrix is $3 \times 3$ .

Step 1.3.2

Multiply each row in the first matrix by each column in the second matrix.

$[\begin{array}{c} 2 \cdot 1 - 6 \cdot 3 + 0 \cdot - 1 & 2 \cdot 1 - 6 \cdot 0 + 0 \cdot 3 & 2 \cdot - 2 - 6 \cdot 4 + 0 \cdot 2 \\ 8 \cdot 1 + 10 \cdot 3 + 2 \cdot - 1 & 8 \cdot 1 + 10 \cdot 0 + 2 \cdot 3 & 8 \cdot - 2 + 10 \cdot 4 + 2 \cdot 2 \\ 6 \cdot 1 + 16 \cdot 3 + 0 \cdot - 1 & 6 \cdot 1 + 16 \cdot 0 + 0 \cdot 3 & 6 \cdot - 2 + 16 \cdot 4 + 0 \cdot 2 \end{array}] + [\begin{array}{c} 2 & 0 & - 2 \\ 4 & 7 & - 5 \\ 1 & 0 & - 1 \end{array}] \cdot [\begin{array}{c} 2 & 0 & - 2 \\ 4 & 7 & - 5 \\ 1 & 0 & - 1 \end{array}]$

Step 1.3.3

Simplify each element of the matrix by multiplying out all the expressions.

$[\begin{array}{c} - 16 & 2 & - 28 \\ 36 & 14 & 28 \\ 54 & 6 & 52 \end{array}] + [\begin{array}{c} 2 & 0 & - 2 \\ 4 & 7 & - 5 \\ 1 & 0 & - 1 \end{array}] \cdot [\begin{array}{c} 2 & 0 & - 2 \\ 4 & 7 & - 5 \\ 1 & 0 & - 1 \end{array}]$

Step 1.4

Multiply $[\begin{array}{c} 2 & 0 & - 2 \\ 4 & 7 & - 5 \\ 1 & 0 & - 1 \end{array}] [\begin{array}{c} 2 & 0 & - 2 \\ 4 & 7 & - 5 \\ 1 & 0 & - 1 \end{array}]$ .

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Step 1.4.1

Step 1.4.2

Multiply each row in the first matrix by each column in the second matrix.

$[\begin{array}{c} - 16 & 2 & - 28 \\ 36 & 14 & 28 \\ 54 & 6 & 52 \end{array}] + [\begin{array}{c} 2 \cdot 2 + 0 \cdot 4 - 2 \cdot 1 & 2 \cdot 0 + 0 \cdot 7 - 2 \cdot 0 & 2 \cdot - 2 + 0 \cdot - 5 - 2 \cdot - 1 \\ 4 \cdot 2 + 7 \cdot 4 - 5 \cdot 1 & 4 \cdot 0 + 7 \cdot 7 - 5 \cdot 0 & 4 \cdot - 2 + 7 \cdot - 5 - 5 \cdot - 1 \\ 1 \cdot 2 + 0 \cdot 4 - 1 \cdot 1 & 1 \cdot 0 + 0 \cdot 7 - 0 & 1 \cdot - 2 + 0 \cdot - 5 - - 1 \end{array}]$

Step 1.4.3

Simplify each element of the matrix by multiplying out all the expressions.

$[\begin{array}{c} - 16 & 2 & - 28 \\ 36 & 14 & 28 \\ 54 & 6 & 52 \end{array}] + [\begin{array}{c} 2 & 0 & - 2 \\ 31 & 49 & - 38 \\ 1 & 0 & - 1 \end{array}]$

Step 2

Add the corresponding elements.

$[\begin{array}{c} - 16 + 2 & 2 + 0 & - 28 - 2 \\ 36 + 31 & 14 + 49 & 28 - 38 \\ 54 + 1 & 6 + 0 & 52 - 1 \end{array}]$

Step 3

Simplify each element.

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Step 3.1

Add $- 16$ and $2$ .

$[\begin{array}{c} - 14 & 2 + 0 & - 28 - 2 \\ 36 + 31 & 14 + 49 & 28 - 38 \\ 54 + 1 & 6 + 0 & 52 - 1 \end{array}]$

Step 3.2

Add $2$ and $0$ .

$[\begin{array}{c} - 14 & 2 & - 28 - 2 \\ 36 + 31 & 14 + 49 & 28 - 38 \\ 54 + 1 & 6 + 0 & 52 - 1 \end{array}]$

Step 3.3

Subtract $2$ from $- 28$ .

$[\begin{array}{c} - 14 & 2 & - 30 \\ 36 + 31 & 14 + 49 & 28 - 38 \\ 54 + 1 & 6 + 0 & 52 - 1 \end{array}]$

Step 3.4

Add $36$ and $31$ .

$[\begin{array}{c} - 14 & 2 & - 30 \\ 67 & 14 + 49 & 28 - 38 \\ 54 + 1 & 6 + 0 & 52 - 1 \end{array}]$

Step 3.5

Add $14$ and $49$ .

$[\begin{array}{c} - 14 & 2 & - 30 \\ 67 & 63 & 28 - 38 \\ 54 + 1 & 6 + 0 & 52 - 1 \end{array}]$

Step 3.6

Subtract $38$ from $28$ .

$[\begin{array}{c} - 14 & 2 & - 30 \\ 67 & 63 & - 10 \\ 54 + 1 & 6 + 0 & 52 - 1 \end{array}]$

Step 3.7

Add $54$ and $1$ .

$[\begin{array}{c} - 14 & 2 & - 30 \\ 67 & 63 & - 10 \\ 55 & 6 + 0 & 52 - 1 \end{array}]$

Step 3.8

Add $6$ and $0$ .

$[\begin{array}{c} - 14 & 2 & - 30 \\ 67 & 63 & - 10 \\ 55 & 6 & 52 - 1 \end{array}]$

Step 3.9

Subtract $1$ from $52$ .

$[\begin{array}{c} - 14 & 2 & - 30 \\ 67 & 63 & - 10 \\ 55 & 6 & 51 \end{array}]$