| 81 | × | 25 | = | ( | 25 | + | x | ) | ( | 2 | x | + | 71 | ) |
| 方程左边 = | 2025 |
| 2025 | = | ( | 25 | + | x | ) | ( | 2 | x | + | 71 | ) |
| 方程右边 = | 25 | ( | 2 | x | + | 71 | ) | + | x | ( | 2 | x | + | 71 | ) |
| = | 25 | × | 2 | x | + | 25 | × | 71 | + | x | ( | 2 | x | + | 71 | ) |
| = | 50 | x | + | 1775 | + | x | ( | 2 | x | + | 71 | ) |
| = | 50 | x | + | 1775 | + | x | × | 2 | x | + | x | × | 71 |
| = | 121 | x | + | 1775 | + | x | × | 2 | x |
| 2025 | = | 121 | x | + | 1775 | + | x | × | 2 | x |
| x1= | - | 125 2 |
| x2=2 |