| ( | - | 100 | x | + | 10000 | ) | ( | x | − | 60 | ) | − | 40000 | = | 0 |
| 方程左边 = | - | 100 | x | ( | x | − | 60 | ) | + | 10000 | ( | x | − | 60 | ) | − | 40000 |
| = | - | 100 | x | x | + | 100 | x | × | 60 | + | 10000 | ( | x | − | 60 | ) | − | 40000 |
| = | - | 100 | x | x | + | 6000 | x | + | 10000 | ( | x | − | 60 | ) | − | 40000 |
| = | - | 100 | x | x | + | 6000 | x | + | 10000 | x | − | 10000 | × | 60 | − | 40000 |
| = | - | 100 | x | x | + | 6000 | x | + | 10000 | x | − | 600000 | − | 40000 |
| = | - | 100 | x | x | + | 16000 | x | − | 640000 |
| - | 100 | x | x | + | 16000 | x | − | 640000 | = | 0 |