| ( | 4 | − | 2 | x | ) | ( | 4 | − | 2 | x | ) | + | 9 | = | 16 | − | 16 | x | + | 4 | x | x | + | 9 |
| 方程左边 = | 4 | ( | 4 | − | 2 | x | ) | − | 2 | x | ( | 4 | − | 2 | x | ) | + | 9 |
| = | 4 | × | 4 | − | 4 | × | 2 | x | − | 2 | x | ( | 4 | − | 2 | x | ) | + | 9 |
| = | 16 | − | 8 | x | − | 2 | x | ( | 4 | − | 2 | x | ) | + | 9 |
| = | 25 | − | 8 | x | − | 2 | x | ( | 4 | − | 2 | x | ) |
| = | 25 | − | 8 | x | − | 2 | x | × | 4 | + | 2 | x | × | 2 | x |
| = | 25 | − | 8 | x | − | 8 | x | + | 4 | x | x |
| = | 25 | − | 16 | x | + | 4 | x | x |
| 25 | − | 16 | x | + | 4 | x | x | = | 16 | − | 16 | x | + | 4 | x | x | + | 9 |
| 方程右边 = | 25 | − | 16 | x | + | 4 | x | x |
| 25 | − | 16 | x | + | 4 | x | x | = | 25 | − | 16 | x | + | 4 | x | x |