Linear Algebra Examples

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

Step 1

Find the reduced row echelon form.

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Step 1.1

Reorder $i$ and $1$ .

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

Step 1.2

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

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Step 1.2.1

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

$[\begin{array}{c} \frac{1 + i}{1 + i} & \frac{2}{1 + i} & \frac{1}{1 + i} & \frac{- i}{1 + i} \\ 1 & i & 2 i & 2 \end{array}]$

Step 1.2.2

Simplify $R_{1}$ .

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

Step 1.3

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

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Step 1.3.1

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

$[\begin{array}{c} 1 & 1 - i & \frac{1}{2} - \frac{i}{2} & - \frac{1}{2} - \frac{i}{2} \\ 1 - 1 & i - (1 - i) & 2 i - (\frac{1}{2} - \frac{i}{2}) & 2 - (- \frac{1}{2} - \frac{i}{2}) \end{array}]$

Step 1.3.2

Simplify $R_{2}$ .

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

Step 1.4

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

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Step 1.4.1

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

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

Step 1.4.2

Simplify $R_{2}$ .

$[\begin{array}{c} 1 & 1 - i & \frac{1}{2} - \frac{i}{2} & - \frac{1}{2} - \frac{i}{2} \\ 0 & 1 & \frac{11}{10} - \frac{3 i}{10} & - \frac{3}{10} - \frac{11 i}{10} \end{array}]$

Step 1.5

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

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Step 1.5.1

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

$[\begin{array}{c} 1 - (1 - i) \cdot 0 & 1 - i - (1 - i) \cdot 1 & \frac{1}{2} - \frac{i}{2} - (1 - i) (\frac{11}{10} - \frac{3 i}{10}) & - \frac{1}{2} - \frac{i}{2} - (1 - i) (- \frac{3}{10} - \frac{11 i}{10}) \\ 0 & 1 & \frac{11}{10} - \frac{3 i}{10} & - \frac{3}{10} - \frac{11 i}{10} \end{array}]$

Step 1.5.2

Simplify $R_{1}$ .

$[\begin{array}{c} 1 & 0 & - \frac{3}{10} + \frac{9 i}{10} & \frac{9}{10} + \frac{3 i}{10} \\ 0 & 1 & \frac{11}{10} - \frac{3 i}{10} & - \frac{3}{10} - \frac{11 i}{10} \end{array}]$

Step 2

The pivot positions are the locations with the leading $1$ in each row. The pivot columns are the columns that have a pivot position.

Pivot Positions: $a_{11}$ and $a_{22}$

Pivot Columns: $1$ and $2$

Step 3

The rank is the number of pivot columns.

$2$