| ( | 6 | x | − | 9 | ) | ( | 6 | x | − | 9 | ) | = | 0 |
| 方程左边 = | 6 | x | ( | 6 | x | − | 9 | ) | − | 9 | ( | 6 | x | − | 9 | ) |
| = | 6 | x | × | 6 | x | − | 6 | x | × | 9 | − | 9 | ( | 6 | x | − | 9 | ) |
| = | 36 | x | x | − | 54 | x | − | 9 | ( | 6 | x | − | 9 | ) |
| = | 36 | x | x | − | 54 | x | − | 9 | × | 6 | x | + | 9 | × | 9 |
| = | 36 | x | x | − | 54 | x | − | 54 | x | + | 81 |
| = | 36 | x | x | − | 108 | x | + | 81 |
| 36 | x | x | − | 108 | x | + | 81 | = | 0 |
| x1= | 3 2 |
| x2= | 3 2 |