| ( | x | − | 1 20 | ) | ( | x | + | 7 5000 | ) | = | 1 20 | × | 7 5000 |
| 方程左边 = | x | ( | x | + | 7 5000 | ) | − | 1 20 | ( | x | + | 7 5000 | ) |
| = | x | x | + | x | × | 7 5000 | − | 1 20 | ( | x | + | 7 5000 | ) |
| = | x | x | + | 7 5000 | x | − | 1 20 | x | − | 1 20 | × | 7 5000 |
| = | x | x | + | 7 5000 | x | − | 1 20 | x | − | 7 100000 |
| = | x | x | − | 243 5000 | x | − | 7 100000 |
| x | x | − | 243 5000 | x | − | 7 100000 | = | 1 20 | × | 7 5000 |
| 方程右边 = | 7 100000 |
| x | x | − | 243 5000 | x | − | 7 100000 | = | 7 100000 |