| 1 | − | 3 | a | ( | 1 | − | a | ( | 1 | − | 3 | a | ) | ) | = | 1 | − | 3 | a | ( | 1 | − | a | ) |
| Left side of the equation = | 1 | − | 3 | a | × | 1 | + | 3 | a | a | ( | 1 | − | 3 | a | ) |
| = | 1 | − | 3 | a | + | 3 | a | a | ( | 1 | − | 3 | a | ) |
| = | 1 | − | 3 | a | + | 3 | a | a | × | 1 | − | 3 | a | a | × | 3 | a |
| = | 1 | − | 3 | a | + | 3 | a | a | − | 9 | a | a | a |
| 1 | − | 3 | a | + | 3 | a | a | − | 9 | a | a | a | = | 1 | − | 3 | a | ( | 1 | − | a | ) |
| Right side of the equation = | 1 | − | 3 | a | × | 1 | + | 3 | a | a |
| = | 1 | − | 3 | a | + | 3 | a | a |
| 1 | − | 3 | a | + | 3 | a | a | − | 9 | a | a | a | = | 1 | − | 3 | a | + | 3 | a | a |