| 3 | = | ( | - | 2 | a | − | 1 | ) | ( | 1 | − | 2 | a | ) |
| Right side of the equation = | - | 2 | a | ( | 1 | − | 2 | a | ) | − | 1 | ( | 1 | − | 2 | a | ) |
| = | - | 2 | a | × | 1 | + | 2 | a | × | 2 | a | − | 1 | ( | 1 | − | 2 | a | ) |
| = | - | 2 | a | + | 4 | a | a | − | 1 | ( | 1 | − | 2 | a | ) |
| = | - | 2 | a | + | 4 | a | a | − | 1 | × | 1 | + | 1 | × | 2 | a |
| = | - | 2 | a | + | 4 | a | a | − | 1 | + | 2 | a |
| = | - | 0 | a | + | 4 | a | a | − | 1 |
| 3 | = | 4 | a | a | − | 1 |