| ( | 3 10 | − | x | ) | ( | 1 4 | − | x | ) | = | 2700 | ( | 1 10 | + | x | ) |
| 方程左边 = | 3 10 | ( | 1 4 | − | x | ) | − | x | ( | 1 4 | − | x | ) |
| = | 3 10 | × | 1 4 | − | 3 10 | x | − | x | ( | 1 4 | − | x | ) |
| = | 3 40 | − | 3 10 | x | − | x | ( | 1 4 | − | x | ) |
| = | 3 40 | − | 3 10 | x | − | x | × | 1 4 | + | x | x |
| = | 3 40 | − | 11 20 | x | + | x | x |
3 40 | − | 11 20 | x | + | x | x | = | 2700 | ( | 1 10 | + | x | ) |
| 方程右边 = | 2700 | × | 1 10 | + | 2700 | x |
| = | 270 | + | 2700 | x |
3 40 | − | 11 20 | x | + | x | x | = | 270 | + | 2700 | x |