| ( | 2 | x | + | 6 | ) | ( | 2 | x | + | 3 | ) | = | 40 |
| 方程左边 = | 2 | x | ( | 2 | x | + | 3 | ) | + | 6 | ( | 2 | x | + | 3 | ) |
| = | 2 | x | × | 2 | x | + | 2 | x | × | 3 | + | 6 | ( | 2 | x | + | 3 | ) |
| = | 4 | x | x | + | 6 | x | + | 6 | ( | 2 | x | + | 3 | ) |
| = | 4 | x | x | + | 6 | x | + | 6 | × | 2 | x | + | 6 | × | 3 |
| = | 4 | x | x | + | 6 | x | + | 12 | x | + | 18 |
| = | 4 | x | x | + | 18 | x | + | 18 |
| 4 | x | x | + | 18 | x | + | 18 | = | 40 |
| x1= | - | 11 2 |
| x2=1 |