| 2 | ( | a | − | 3 | ) | ( | a | − | 3 | ) | − | 4 | a | + | 12 | = | 0 |
| 方程左边 = | 2 | a | ( | a | − | 3 | ) | − | 2 | × | 3 | ( | a | − | 3 | ) | − | 4 | a | + | 12 |
| = | 2 | a | ( | a | − | 3 | ) | − | 6 | ( | a | − | 3 | ) | − | 4 | a | + | 12 |
| = | 2 | a | a | − | 2 | a | × | 3 | − | 6 | ( | a | − | 3 | ) | − | 4 | a | + | 12 |
| = | 2 | a | a | − | 6 | a | − | 6 | ( | a | − | 3 | ) | − | 4 | a | + | 12 |
| = | 2 | a | a | − | 10 | a | − | 6 | ( | a | − | 3 | ) | + | 12 |
| = | 2 | a | a | − | 10 | a | − | 6 | a | + | 6 | × | 3 | + | 12 |
| = | 2 | a | a | − | 10 | a | − | 6 | a | + | 18 | + | 12 |
| = | 2 | a | a | − | 16 | a | + | 30 |
| 2 | a | a | − | 16 | a | + | 30 | = | 0 |