Example ¹2. Finding the Determinant of a 4x4 MatrixThis solution was made using the calculator presented on the site.
Let's calculate the determinant A using a elementary transformations.
| det A = |
| 4 | 6 | -2 | 4 | | = | | 1 | 2 | -3 | 1 | | 4 | -2 | 1 | 0 | | 6 | 4 | 4 | 6 | The elements of column 1 multiplied by -1 are added to the corresponding elements of column 4. more info
| 4 | 6 | -2 | 4 + 4 * ( -1) | | | 1 | 2 | -3 | 1 + 1 * ( -1) | | 4 | -2 | 1 | 0 + 4 * ( -1) | | 6 | 4 | 4 | 6 + 6 * ( -1) | This elementary transformation does not change the value of the determinant.
| = |
| 4 | 6 | -2 | 0 | | = | | 1 | 2 | -3 | 0 | | 4 | -2 | 1 | -4 | | 6 | 4 | 4 | 0 | Expand the determinant along the column 4. more info
| 4 | 6 | -2 | 0 | | | 1 | 2 | -3 | 0 | | 4 | -2 | 1 | -4 | | 6 | 4 | 4 | 0 | |
Row number 1 Column number 4 |
|
Element |
|
Row 1 and column 4 have been deleted |
| ( -1) 1 + 4 |
* |
0 |
* |
|
| 4 | 6 | -2 | 0 | | | 1 | 2 | -3 | 0 | | 4 | -2 | 1 | -4 | | 6 | 4 | 4 | 0 | |
Row number 2 Column number 4 |
|
Element |
|
Row 2 and column 4 have been deleted |
| ( -1) 2 + 4 |
* |
0 |
* |
|
| 4 | 6 | -2 | 0 | | | 1 | 2 | -3 | 0 | | 4 | -2 | 1 | -4 | | 6 | 4 | 4 | 0 | |
Row number 3 Column number 4 |
|
Element |
|
Row 3 and column 4 have been deleted |
| ( -1) 3 + 4 |
* |
-4 |
* |
|
| 4 | 6 | -2 | 0 | | | 1 | 2 | -3 | 0 | | 4 | -2 | 1 | -4 | | 6 | 4 | 4 | 0 | |
Row number 4 Column number 4 |
|
Element |
|
Row 4 and column 4 have been deleted |
| ( -1) 4 + 4 |
* |
0 |
* |
|
Products are summed. If the element is zero then product is zero too.
| = ( -1) 3 + 4 * ( -4) * |
| 4 | 6 | -2 | | = | | 1 | 2 | -3 | | 6 | 4 | 4 |
| = 4 * |
| 4 | 6 | -2 | | = | | 1 | 2 | -3 | | 6 | 4 | 4 | The elements of column 1 multiplied by -1 are added to the corresponding elements of column 2. more info
| 4 | 6 + 4 * ( -1) | -2 | | | 1 | 2 + 1 * ( -1) | -3 | | 6 | 4 + 6 * ( -1) | 4 | This elementary transformation does not change the value of the determinant.
| = 4 * |
| 4 | 2 | -2 | | = | | 1 | 1 | -3 | | 6 | -2 | 4 | The elements of column 2 multiplied by -2 are added to the corresponding elements of column 1. more info
| 4 + 2 * ( -2) | 2 | -2 | | | 1 + 1 * ( -2) | 1 | -3 | | 6 + ( -2) * ( -2) | -2 | 4 | This elementary transformation does not change the value of the determinant.
| = 4 * |
| 0 | 2 | -2 | | = | | -1 | 1 | -3 | | 10 | -2 | 4 | The elements of column 2 are added to the corresponding elements of column 3. more info
| 0 | 2 | -2 + 2 | | | -1 | 1 | -3 + 1 | | 10 | -2 | 4 + ( -2) | This elementary transformation does not change the value of the determinant.
| = 4 * |
| 0 | 2 | 0 | | = | | -1 | 1 | -2 | | 10 | -2 | 2 | Expand the determinant along the row 1. more info
|
Row number 1 Column number 1 |
|
Element |
|
Row 1 and column 1 have been deleted |
| ( -1) 1 + 1 |
* |
0 |
* |
|
|
Row number 1 Column number 2 |
|
Element |
|
Row 1 and column 2 have been deleted |
| ( -1) 1 + 2 |
* |
2 |
* |
|
|
Row number 1 Column number 3 |
|
Element |
|
Row 1 and column 3 have been deleted |
| ( -1) 1 + 3 |
* |
0 |
* |
|
Products are summed. If the element is zero then product is zero too.
| = 4 * ( -1) 1 + 2 * 2 * |
| -1 | -2 | | = | | 10 | 2 | = - 8 * ( -1 * 2 - ( -2) * 10 ) = = -144
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