| ( | 2 | x | + | 4 | ) | ( | 2 | x | + | 4 | ) | + | 2 | ( | 2 | x | + | 4 | ) | − | 8 | = | - | 4 | − | x |
| 方程左边 = | 2 | x | ( | 2 | x | + | 4 | ) | + | 4 | ( | 2 | x | + | 4 | ) | + | 2 | ( | 2 | x | + | 4 | ) | − | 8 |
| = | 2 | x | × | 2 | x | + | 2 | x | × | 4 | + | 4 | ( | 2 | x | + | 4 | ) | + | 2 | ( | 2 | x | + | 4 | ) | − | 8 |
| = | 4 | x | x | + | 8 | x | + | 4 | ( | 2 | x | + | 4 | ) | + | 2 | ( | 2 | x | + | 4 | ) | − | 8 |
| = | 4 | x | x | + | 8 | x | + | 4 | × | 2 | x | + | 4 | × | 4 | + | 2 | ( | 2 | x | + | 4 | ) |
| = | 4 | x | x | + | 8 | x | + | 8 | x | + | 16 | + | 2 | ( | 2 | x | + | 4 | ) | − | 8 |
| = | 4 | x | x | + | 16 | x | + | 8 | + | 2 | ( | 2 | x | + | 4 | ) |
| = | 4 | x | x | + | 16 | x | + | 8 | + | 2 | × | 2 | x | + | 2 | × | 4 |
| = | 4 | x | x | + | 16 | x | + | 8 | + | 4 | x | + | 8 |
| = | 4 | x | x | + | 20 | x | + | 16 |
| 4 | x | x | + | 20 | x | + | 16 | = | - | 4 | − | x |
| x2= | - | 5 4 |