| ( | x | − | 4 | ) | ( | 500 | − | 10 | ( | x | − | 5 | ) | ) | = | 4100 |
| 方程左边 = | x | ( | 500 | − | 10 | ( | x | − | 5 | ) | ) | − | 4 | ( | 500 | − | 10 | ( | x | − | 5 | ) | ) |
| = | x | × | 500 | − | x | × | 10 | ( | x | − | 5 | ) | − | 4 | ( | 500 | − | 10 | ( | x | − | 5 | ) | ) |
| = | 500 | x | − | x | × | 10 | x | + | x | × | 10 | × | 5 | − | 4 | ( | 500 | − | 10 | ( | x | − | 5 | ) | ) |
| = | 500 | x | − | x | × | 10 | x | + | x | × | 50 | − | 4 | ( | 500 | − | 10 | ( | x | − | 5 | ) | ) |
| = | 550 | x | − | x | × | 10 | x | − | 4 | ( | 500 | − | 10 | ( | x | − | 5 | ) | ) |
| = | 550 | x | − | x | × | 10 | x | − | 4 | × | 500 | + | 4 | × | 10 | ( | x | − | 5 | ) |
| = | 550 | x | − | x | × | 10 | x | − | 2000 | + | 40 | ( | x | − | 5 | ) |
| = | 550 | x | − | x | × | 10 | x | − | 2000 | + | 40 | x | − | 40 | × | 5 |
| = | 550 | x | − | x | × | 10 | x | − | 2000 | + | 40 | x | − | 200 |
| = | 590 | x | − | x | × | 10 | x | − | 2200 |
| 590 | x | − | x | × | 10 | x | − | 2200 | = | 4100 |