| ( | X | − | 21 20 | ) | ( | X | − | 107 100 | ) | = | 0 |
| 方程左边 = | X | ( | X | − | 107 100 | ) | − | 21 20 | ( | X | − | 107 100 | ) |
| = | X | X | − | X | × | 107 100 | − | 21 20 | ( | X | − | 107 100 | ) |
| = | X | X | − | 107 100 | X | − | 21 20 | X | + | 21 20 | × | 107 100 |
| = | X | X | − | 107 100 | X | − | 21 20 | X | + | 2247 2000 |
| = | X | X | − | 53 25 | X | + | 2247 2000 |
| X | X | − | 53 25 | X | + | 2247 2000 | = | 0 |