| 5 | ( | 2 | x | − | 10 | ) | ( | x | − | 10 | ) | = | 3000 |
| 方程左边 = | 5 | × | 2 | x | ( | x | − | 10 | ) | − | 5 | × | 10 | ( | x | − | 10 | ) |
| = | 10 | x | ( | x | − | 10 | ) | − | 50 | ( | x | − | 10 | ) |
| = | 10 | x | x | − | 10 | x | × | 10 | − | 50 | ( | x | − | 10 | ) |
| = | 10 | x | x | − | 100 | x | − | 50 | ( | x | − | 10 | ) |
| = | 10 | x | x | − | 100 | x | − | 50 | x | + | 50 | × | 10 |
| = | 10 | x | x | − | 100 | x | − | 50 | x | + | 500 |
| = | 10 | x | x | − | 150 | x | + | 500 |
| 10 | x | x | − | 150 | x | + | 500 | = | 3000 |