| X | − | 1 | ( | ( | X | − | 2 | ) | ( | X | − | 5 | ) | ) | = | 0 |
| 方程左边 = | X | − | 1 | ( | X | − | 2 | ) | ( | X | − | 5 | ) |
| = | X | − | 1 | X | ( | X | − | 5 | ) | + | 1 | × | 2 | ( | X | − | 5 | ) |
| = | X | − | 1 | X | ( | X | − | 5 | ) | + | 2 | ( | X | − | 5 | ) |
| = | X | − | 1 | X | X | + | 1 | X | × | 5 | + | 2 | ( | X | − | 5 | ) |
| = | X | − | 1 | X | X | + | 5 | X | + | 2 | ( | X | − | 5 | ) |
| = | 6 | X | − | 1 | X | X | + | 2 | ( | X | − | 5 | ) |
| = | 6 | X | − | 1 | X | X | + | 2 | X | − | 2 | × | 5 |
| = | 6 | X | − | 1 | X | X | + | 2 | X | − | 10 |
| = | 8 | X | − | 1 | X | X | − | 10 |
| 8 | X | − | 1 | X | X | − | 10 | = | 0 |