Linear Algebra Examples

$[\begin{array}{c} 1 & - 1 \\ - 2 & 1 \\ 3 & 1 \end{array}] [\begin{array}{c} \frac{15}{14} \\ 4 \end{array}] - [\begin{array}{c} 1 \\ 5 \\ 8 \end{array}]$

Step 1

Multiply $[\begin{array}{c} 1 & - 1 \\ - 2 & 1 \\ 3 & 1 \end{array}] [\begin{array}{c} \frac{15}{14} \\ 4 \end{array}]$ .

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Step 1.1

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 $3 \times 2$ and the second matrix is $2 \times 1$ .

Step 1.2

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

$[\begin{array}{c} 1 (\frac{15}{14}) - 1 \cdot 4 \\ - 2 (\frac{15}{14}) + 1 \cdot 4 \\ 3 (\frac{15}{14}) + 1 \cdot 4 \end{array}] - [\begin{array}{c} 1 \\ 5 \\ 8 \end{array}]$

Step 1.3

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

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Step 1.3.1

Multiply $4$ by $14$ .

$[\begin{array}{c} - \frac{41}{14} \\ \frac{13}{7} \\ \frac{45 + 56}{14} \end{array}] - [\begin{array}{c} 1 \\ 5 \\ 8 \end{array}]$

Step 1.3.2

Add $45$ and $56$ .

$[\begin{array}{c} - \frac{41}{14} \\ \frac{13}{7} \\ \frac{101}{14} \end{array}] - [\begin{array}{c} 1 \\ 5 \\ 8 \end{array}]$

Step 2

Subtract the corresponding elements.

$[\begin{array}{c} - \frac{41}{14} - 1 \\ \frac{13}{7} - 5 \\ \frac{101}{14} - 8 \end{array}]$

Step 3

Simplify each element.

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Step 3.1

To write $- 1$ as a fraction with a common denominator, multiply by $\frac{14}{14}$ .

$[\begin{array}{c} - \frac{41}{14} - 1 \cdot \frac{14}{14} \\ \frac{13}{7} - 5 \\ \frac{101}{14} - 8 \end{array}]$

Step 3.2

Combine $- 1$ and $\frac{14}{14}$ .

$[\begin{array}{c} - \frac{41}{14} + \frac{- 1 \cdot 14}{14} \\ \frac{13}{7} - 5 \\ \frac{101}{14} - 8 \end{array}]$

Step 3.3

Combine the numerators over the common denominator.

$[\begin{array}{c} \frac{- 41 - 1 \cdot 14}{14} \\ \frac{13}{7} - 5 \\ \frac{101}{14} - 8 \end{array}]$

Step 3.4

Simplify the numerator.

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Step 3.4.1

Multiply $- 1$ by $14$ .

$[\begin{array}{c} \frac{- 41 - 14}{14} \\ \frac{13}{7} - 5 \\ \frac{101}{14} - 8 \end{array}]$

Step 3.4.2

Subtract $14$ from $- 41$ .

$[\begin{array}{c} \frac{- 55}{14} \\ \frac{13}{7} - 5 \\ \frac{101}{14} - 8 \end{array}]$

Step 3.5

Move the negative in front of the fraction.

$[\begin{array}{c} - \frac{55}{14} \\ \frac{13}{7} - 5 \\ \frac{101}{14} - 8 \end{array}]$

Step 3.6

To write $- 5$ as a fraction with a common denominator, multiply by $\frac{7}{7}$ .

$[\begin{array}{c} - \frac{55}{14} \\ \frac{13}{7} - 5 \cdot \frac{7}{7} \\ \frac{101}{14} - 8 \end{array}]$

Step 3.7

Combine $- 5$ and $\frac{7}{7}$ .

$[\begin{array}{c} - \frac{55}{14} \\ \frac{13}{7} + \frac{- 5 \cdot 7}{7} \\ \frac{101}{14} - 8 \end{array}]$

Step 3.8

Combine the numerators over the common denominator.

$[\begin{array}{c} - \frac{55}{14} \\ \frac{13 - 5 \cdot 7}{7} \\ \frac{101}{14} - 8 \end{array}]$

Step 3.9

Simplify the numerator.

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Step 3.9.1

Multiply $- 5$ by $7$ .

$[\begin{array}{c} - \frac{55}{14} \\ \frac{13 - 35}{7} \\ \frac{101}{14} - 8 \end{array}]$

Step 3.9.2

Subtract $35$ from $13$ .

$[\begin{array}{c} - \frac{55}{14} \\ \frac{- 22}{7} \\ \frac{101}{14} - 8 \end{array}]$

Step 3.10

Move the negative in front of the fraction.

$[\begin{array}{c} - \frac{55}{14} \\ - \frac{22}{7} \\ \frac{101}{14} - 8 \end{array}]$

Step 3.11

To write $- 8$ as a fraction with a common denominator, multiply by $\frac{14}{14}$ .

$[\begin{array}{c} - \frac{55}{14} \\ - \frac{22}{7} \\ \frac{101}{14} - 8 \cdot \frac{14}{14} \end{array}]$

Step 3.12

Combine $- 8$ and $\frac{14}{14}$ .

$[\begin{array}{c} - \frac{55}{14} \\ - \frac{22}{7} \\ \frac{101}{14} + \frac{- 8 \cdot 14}{14} \end{array}]$

Step 3.13

Combine the numerators over the common denominator.

$[\begin{array}{c} - \frac{55}{14} \\ - \frac{22}{7} \\ \frac{101 - 8 \cdot 14}{14} \end{array}]$

Step 3.14

Simplify the numerator.

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Step 3.14.1

Multiply $- 8$ by $14$ .

$[\begin{array}{c} - \frac{55}{14} \\ - \frac{22}{7} \\ \frac{101 - 112}{14} \end{array}]$

Step 3.14.2

Subtract $112$ from $101$ .

$[\begin{array}{c} - \frac{55}{14} \\ - \frac{22}{7} \\ \frac{- 11}{14} \end{array}]$

Step 3.15

Move the negative in front of the fraction.

$[\begin{array}{c} - \frac{55}{14} \\ - \frac{22}{7} \\ - \frac{11}{14} \end{array}]$