| ( | 6 | x | − | 12 5 | ) | ( | 5 | x | − | 2 | ) | = | 9 5 |
| 方程左边 = | 6 | x | ( | 5 | x | − | 2 | ) | − | 12 5 | ( | 5 | x | − | 2 | ) |
| = | 6 | x | × | 5 | x | − | 6 | x | × | 2 | − | 12 5 | ( | 5 | x | − | 2 | ) |
| = | 30 | x | x | − | 12 | x | − | 12 5 | ( | 5 | x | − | 2 | ) |
| = | 30 | x | x | − | 12 | x | − | 12 5 | × | 5 | x | + | 12 5 | × | 2 |
| = | 30 | x | x | − | 12 | x | − | 12 | x | + | 24 5 |
| = | 30 | x | x | − | 24 | x | + | 24 5 |
| 30 | x | x | − | 24 | x | + | 24 5 | = | 9 5 |