| 25 | ( | x | + | 1 | ) | + | 25 | ( | x | + | 1 | ) | ( | x | + | 1 | ) | = | 66 |
| 方程左边 = | 25 | x | + | 25 | × | 1 | + | 25 | ( | x | + | 1 | ) | ( | x | + | 1 | ) |
| = | 25 | x | + | 25 | + | 25 | ( | x | + | 1 | ) | ( | x | + | 1 | ) |
| = | 25 | x | + | 25 | + | 25 | x | ( | x | + | 1 | ) | + | 25 | × | 1 | ( | x | + | 1 | ) |
| = | 25 | x | + | 25 | + | 25 | x | ( | x | + | 1 | ) | + | 25 | ( | x | + | 1 | ) |
| = | 25 | x | + | 25 | + | 25 | x | x | + | 25 | x | × | 1 | + | 25 | ( | x | + | 1 | ) |
| = | 25 | x | + | 25 | + | 25 | x | x | + | 25 | x | + | 25 | ( | x | + | 1 | ) |
| = | 50 | x | + | 25 | + | 25 | x | x | + | 25 | ( | x | + | 1 | ) |
| = | 50 | x | + | 25 | + | 25 | x | x | + | 25 | x | + | 25 | × | 1 |
| = | 50 | x | + | 25 | + | 25 | x | x | + | 25 | x | + | 25 |
| = | 75 | x | + | 50 | + | 25 | x | x |
| 75 | x | + | 50 | + | 25 | x | x | = | 66 |
| x1= | - | 16 5 |
| x2= | 1 5 |