| ( | - | 30 | − | x | ) | ( | 25 | − | x | ) | + | 22 | × | 33 | = | 0 |
| 方程左边 = | ( | - | 30 | − | x | ) | ( | 25 | − | x | ) | + | 726 |
| ( | - | 30 | − | x | ) | ( | 25 | − | x | ) | + | 726 | = | 0 |
| 方程左边 = | - | 30 | ( | 25 | − | x | ) | − | x | ( | 25 | − | x | ) | + | 726 |
| = | - | 30 | × | 25 | + | 30 | x | − | x | ( | 25 | − | x | ) | + | 726 |
| = | - | 750 | + | 30 | x | − | x | ( | 25 | − | x | ) | + | 726 |
| = | - | 24 | + | 30 | x | − | x | ( | 25 | − | x | ) |
| = | - | 24 | + | 30 | x | − | x | × | 25 | + | x | x |
| = | - | 24 | + | 5 | x | + | x | x |
| - | 24 | + | 5 | x | + | x | x | = | 0 |