| ( | 57 | − | 8 | x | ) | ( | 1 20 | + | x | ) | = | 849 100 |
| 方程左边 = | 57 | ( | 1 20 | + | x | ) | − | 8 | x | ( | 1 20 | + | x | ) |
| = | 57 | × | 1 20 | + | 57 | x | − | 8 | x | ( | 1 20 | + | x | ) |
| = | 57 20 | + | 57 | x | − | 8 | x | ( | 1 20 | + | x | ) |
| = | 57 20 | + | 57 | x | − | 8 | x | × | 1 20 | − | 8 | x | x |
| = | 57 20 | + | 57 | x | − | 2 5 | x | − | 8 | x | x |
| = | 57 20 | + | 283 5 | x | − | 8 | x | x |
57 20 | + | 283 5 | x | − | 8 | x | x | = | 849 100 |