| 16 | − | 4 | ( | a | + | 2 | ) | ( | a | − | 1 | ) | = | 0 |
| 方程左边 = | 16 | − | 4 | a | ( | a | − | 1 | ) | − | 4 | × | 2 | ( | a | − | 1 | ) |
| = | 16 | − | 4 | a | ( | a | − | 1 | ) | − | 8 | ( | a | − | 1 | ) |
| = | 16 | − | 4 | a | a | + | 4 | a | × | 1 | − | 8 | ( | a | − | 1 | ) |
| = | 16 | − | 4 | a | a | + | 4 | a | − | 8 | ( | a | − | 1 | ) |
| = | 16 | − | 4 | a | a | + | 4 | a | − | 8 | a | + | 8 | × | 1 |
| = | 16 | − | 4 | a | a | + | 4 | a | − | 8 | a | + | 8 |
| = | 24 | − | 4 | a | a | − | 4 | a |
| 24 | − | 4 | a | a | − | 4 | a | = | 0 |