| - | 2 | ( | 3 | x | + | 1 | ) | ( | 7 | x | + | 11 | ) | = | 0 |
| 方程左边 = | - | 2 | × | 3 | x | ( | 7 | x | + | 11 | ) | − | 2 | × | 1 | ( | 7 | x | + | 11 | ) |
| = | - | 6 | x | ( | 7 | x | + | 11 | ) | − | 2 | ( | 7 | x | + | 11 | ) |
| = | - | 6 | x | × | 7 | x | − | 6 | x | × | 11 | − | 2 | ( | 7 | x | + | 11 | ) |
| = | - | 42 | x | x | − | 66 | x | − | 2 | ( | 7 | x | + | 11 | ) |
| = | - | 42 | x | x | − | 66 | x | − | 2 | × | 7 | x | − | 2 | × | 11 |
| = | - | 42 | x | x | − | 66 | x | − | 14 | x | − | 22 |
| = | - | 42 | x | x | − | 80 | x | − | 22 |
| - | 42 | x | x | − | 80 | x | − | 22 | = | 0 |
| x1= | - | 11 7 |
| x2= | - | 1 3 |