| ( | 52 | − | 2 | x | ) | ( | 28 | ÷ | 2 | × | x | + | 1 | ) | = | 640 |
| 方程左边 = | 52 | ( | 28 | ÷ | 2 | × | x | + | 1 | ) | − | 2 | x | ( | 28 | ÷ | 2 | × | x | + | 1 | ) |
| = | 52 | × | 28 | ÷ | 2 | × | x | + | 52 | × | 1 | − | 2 | x | ( | 28 | ÷ | 2 | × | x | + | 1 | ) |
| = | 728 | x | + | 52 | − | 2 | x | ( | 28 | ÷ | 2 | × | x | + | 1 | ) |
| = | 728 | x | + | 52 | − | 2 | x | × | 28 | ÷ | 2 | × | x | − | 2 | x | × | 1 |
| = | 728 | x | + | 52 | − | 28 | x | x | − | 2 | x |
| = | 726 | x | + | 52 | − | 28 | x | x |
| 726 | x | + | 52 | − | 28 | x | x | = | 640 |