Precalculus Examples

$[\begin{array}{c} 2 & 7 & 15 & - 12 \\ 4 & 7 & 13 & - 10 \\ 3 & 6 & 12 & - 9 \end{array}]$

Step 1

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

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Step 1.1

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

$[\begin{array}{c} \frac{2}{2} & \frac{7}{2} & \frac{15}{2} & \frac{- 12}{2} \\ 4 & 7 & 13 & - 10 \\ 3 & 6 & 12 & - 9 \end{array}]$

Step 1.2

Simplify $R_{1}$ .

$[\begin{array}{c} 1 & \frac{7}{2} & \frac{15}{2} & - 6 \\ 4 & 7 & 13 & - 10 \\ 3 & 6 & 12 & - 9 \end{array}]$

Step 2

Perform the row operation $R_{2} = R_{2} - 4 R_{1}$ to make the entry at $2, 1$ a $0$ .

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Step 2.1

Perform the row operation $R_{2} = R_{2} - 4 R_{1}$ to make the entry at $2, 1$ a $0$ .

$[\begin{array}{c} 1 & \frac{7}{2} & \frac{15}{2} & - 6 \\ 4 - 4 \cdot 1 & 7 - 4 (\frac{7}{2}) & 13 - 4 (\frac{15}{2}) & - 10 - 4 \cdot - 6 \\ 3 & 6 & 12 & - 9 \end{array}]$

Step 2.2

Simplify $R_{2}$ .

$[\begin{array}{c} 1 & \frac{7}{2} & \frac{15}{2} & - 6 \\ 0 & - 7 & - 17 & 14 \\ 3 & 6 & 12 & - 9 \end{array}]$

Step 3

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

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Step 3.1

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

$[\begin{array}{c} 1 & \frac{7}{2} & \frac{15}{2} & - 6 \\ 0 & - 7 & - 17 & 14 \\ 3 - 3 \cdot 1 & 6 - 3 (\frac{7}{2}) & 12 - 3 (\frac{15}{2}) & - 9 - 3 \cdot - 6 \end{array}]$

Step 3.2

Simplify $R_{3}$ .

$[\begin{array}{c} 1 & \frac{7}{2} & \frac{15}{2} & - 6 \\ 0 & - 7 & - 17 & 14 \\ 0 & - \frac{9}{2} & - \frac{21}{2} & 9 \end{array}]$

Step 4

Multiply each element of $R_{2}$ by $- \frac{1}{7}$ to make the entry at $2, 2$ a $1$ .

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Step 4.1

Multiply each element of $R_{2}$ by $- \frac{1}{7}$ to make the entry at $2, 2$ a $1$ .

$[\begin{array}{c} 1 & \frac{7}{2} & \frac{15}{2} & - 6 \\ - \frac{1}{7} \cdot 0 & - \frac{1}{7} \cdot - 7 & - \frac{1}{7} \cdot - 17 & - \frac{1}{7} \cdot 14 \\ 0 & - \frac{9}{2} & - \frac{21}{2} & 9 \end{array}]$

Step 4.2

Simplify $R_{2}$ .

$[\begin{array}{c} 1 & \frac{7}{2} & \frac{15}{2} & - 6 \\ 0 & 1 & \frac{17}{7} & - 2 \\ 0 & - \frac{9}{2} & - \frac{21}{2} & 9 \end{array}]$

Step 5

Perform the row operation $R_{3} = R_{3} + \frac{9}{2} R_{2}$ to make the entry at $3, 2$ a $0$ .

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Step 5.1

Perform the row operation $R_{3} = R_{3} + \frac{9}{2} R_{2}$ to make the entry at $3, 2$ a $0$ .

$[\begin{array}{c} 1 & \frac{7}{2} & \frac{15}{2} & - 6 \\ 0 & 1 & \frac{17}{7} & - 2 \\ 0 + \frac{9}{2} \cdot 0 & - \frac{9}{2} + \frac{9}{2} \cdot 1 & - \frac{21}{2} + \frac{9}{2} \cdot \frac{17}{7} & 9 + \frac{9}{2} \cdot - 2 \end{array}]$

Step 5.2

Simplify $R_{3}$ .

$[\begin{array}{c} 1 & \frac{7}{2} & \frac{15}{2} & - 6 \\ 0 & 1 & \frac{17}{7} & - 2 \\ 0 & 0 & \frac{3}{7} & 0 \end{array}]$

Step 6

Multiply each element of $R_{3}$ by $\frac{7}{3}$ to make the entry at $3, 3$ a $1$ .

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Step 6.1

Multiply each element of $R_{3}$ by $\frac{7}{3}$ to make the entry at $3, 3$ a $1$ .

$[\begin{array}{c} 1 & \frac{7}{2} & \frac{15}{2} & - 6 \\ 0 & 1 & \frac{17}{7} & - 2 \\ \frac{7}{3} \cdot 0 & \frac{7}{3} \cdot 0 & \frac{7}{3} \cdot \frac{3}{7} & \frac{7}{3} \cdot 0 \end{array}]$

Step 6.2

Simplify $R_{3}$ .

$[\begin{array}{c} 1 & \frac{7}{2} & \frac{15}{2} & - 6 \\ 0 & 1 & \frac{17}{7} & - 2 \\ 0 & 0 & 1 & 0 \end{array}]$

Step 7

Perform the row operation $R_{2} = R_{2} - \frac{17}{7} R_{3}$ to make the entry at $2, 3$ a $0$ .

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Step 7.1

Perform the row operation $R_{2} = R_{2} - \frac{17}{7} R_{3}$ to make the entry at $2, 3$ a $0$ .

$[\begin{array}{c} 1 & \frac{7}{2} & \frac{15}{2} & - 6 \\ 0 - \frac{17}{7} \cdot 0 & 1 - \frac{17}{7} \cdot 0 & \frac{17}{7} - \frac{17}{7} \cdot 1 & - 2 - \frac{17}{7} \cdot 0 \\ 0 & 0 & 1 & 0 \end{array}]$

Step 7.2

Simplify $R_{2}$ .

$[\begin{array}{c} 1 & \frac{7}{2} & \frac{15}{2} & - 6 \\ 0 & 1 & 0 & - 2 \\ 0 & 0 & 1 & 0 \end{array}]$

Step 8

Perform the row operation $R_{1} = R_{1} - \frac{15}{2} R_{3}$ to make the entry at $1, 3$ a $0$ .

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Step 8.1

Perform the row operation $R_{1} = R_{1} - \frac{15}{2} R_{3}$ to make the entry at $1, 3$ a $0$ .

$[\begin{array}{c} 1 - \frac{15}{2} \cdot 0 & \frac{7}{2} - \frac{15}{2} \cdot 0 & \frac{15}{2} - \frac{15}{2} \cdot 1 & - 6 - \frac{15}{2} \cdot 0 \\ 0 & 1 & 0 & - 2 \\ 0 & 0 & 1 & 0 \end{array}]$

Step 8.2

Simplify $R_{1}$ .

$[\begin{array}{c} 1 & \frac{7}{2} & 0 & - 6 \\ 0 & 1 & 0 & - 2 \\ 0 & 0 & 1 & 0 \end{array}]$

Step 9

Perform the row operation $R_{1} = R_{1} - \frac{7}{2} R_{2}$ to make the entry at $1, 2$ a $0$ .

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Step 9.1

Perform the row operation $R_{1} = R_{1} - \frac{7}{2} R_{2}$ to make the entry at $1, 2$ a $0$ .

$[\begin{array}{c} 1 - \frac{7}{2} \cdot 0 & \frac{7}{2} - \frac{7}{2} \cdot 1 & 0 - \frac{7}{2} \cdot 0 & - 6 - \frac{7}{2} \cdot - 2 \\ 0 & 1 & 0 & - 2 \\ 0 & 0 & 1 & 0 \end{array}]$

Step 9.2

Simplify $R_{1}$ .

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