| x | x | − | 6 | x | + | 9 | = | ( | 5 | − | 2 | x | ) | ( | 5 | − | 2 | x | ) |
| 方程右边 = | 5 | ( | 5 | − | 2 | x | ) | − | 2 | x | ( | 5 | − | 2 | x | ) |
| = | 5 | × | 5 | − | 5 | × | 2 | x | − | 2 | x | ( | 5 | − | 2 | x | ) |
| = | 25 | − | 10 | x | − | 2 | x | ( | 5 | − | 2 | x | ) |
| = | 25 | − | 10 | x | − | 2 | x | × | 5 | + | 2 | x | × | 2 | x |
| = | 25 | − | 10 | x | − | 10 | x | + | 4 | x | x |
| = | 25 | − | 20 | x | + | 4 | x | x |
| x | x | − | 6 | x | + | 9 | = | 25 | − | 20 | x | + | 4 | x | x |
| x2= | 8 3 |