| ( | 4000 | + | ( | 100 | − | x | ) | × | 100 | ) | x | − | 500 | x | − | ( | 100 | − | x | ) | × | 100 | = | 404000 |
| 方程左边 = | 4000 | x | + | ( | 100 | − | x | ) | × | 100 | x | − | 500 | x | − | ( | 100 | − | x | ) | × | 100 |
| = | 3500 | x | + | ( | 100 | − | x | ) | × | 100 | x | − | ( | 100 | − | x | ) | × | 100 |
| = | 3500 | x | + | 100 | × | 100 | x | − | x | × | 100 | x | − | ( | 100 | − | x | ) | × | 100 |
| = | 3500 | x | + | 10000 | x | − | x | × | 100 | x | − | ( | 100 | − | x | ) | × | 100 |
| = | 13500 | x | − | x | × | 100 | x | − | ( | 100 | − | x | ) | × | 100 |
| = | 13500 | x | − | x | × | 100 | x | − | 100 | × | 100 | + | x | × | 100 |
| = | 13500 | x | − | x | × | 100 | x | − | 10000 | + | x | × | 100 |
| = | 13600 | x | − | x | × | 100 | x | − | 10000 |
| 13600 | x | − | x | × | 100 | x | − | 10000 | = | 404000 |