The point (4, -1) is represented as:
| 4 |
| |
|-1 |
Please, understand that the three vertical | represent a continuous line, which is the matrix representation.
The traslataion of 3 units to the left and 7 units up means that you have to add the matrix:
|- 3|
| |
|7 |
So the representation is:
|4 | |-3 | |1 |
| | + | | = | |
|-1 | |7 | |6 |
