| 21000 | ÷ | ( | x | + | 450 | ) | − | 10500 | ÷ | x | = | 450 |
| 方程两边同时乘以: | ( | x | + | 450 | ) |
| 21000 | − | 10500 | ÷ | x | × | ( | x | + | 450 | ) | = | 450 | ( | x | + | 450 | ) |
| 21000 | − | 10500 | ÷ | x | × | x | − | 10500 | ÷ | x | × | 450 | = | 450 | ( | x | + | 450 | ) |
| 21000 | − | 10500 | ÷ | x | × | x | − | 10500 | ÷ | x | × | 450 | = | 450 | x | + | 450 | × | 450 |
| 21000 | − | 10500 | ÷ | x | × | x | − | 4725000 | ÷ | x | = | 450 | x | + | 202500 |
| 方程两边同时乘以: | x |
| 21000 | x | − | 10500 | ÷ | 1 | × | 1 | x | − | 4725000 | = | 450 | x | x | + | 202500 | x |