| 20 | ( | 1 | + | x | ) | × | 1000 | ( | 1 | + | x | ) | = | 33800 |
| 方程左边 = | 20000 | ( | 1 | + | x | ) | ( | 1 | + | x | ) |
| 20000 | ( | 1 | + | x | ) | ( | 1 | + | x | ) | = | 33800 |
| 方程左边 = | 20000 | × | 1 | ( | 1 | + | x | ) | + | 20000 | x | ( | 1 | + | x | ) |
| = | 20000 | ( | 1 | + | x | ) | + | 20000 | x | ( | 1 | + | x | ) |
| = | 20000 | × | 1 | + | 20000 | x | + | 20000 | x | ( | 1 | + | x | ) |
| = | 20000 | + | 20000 | x | + | 20000 | x | ( | 1 | + | x | ) |
| = | 20000 | + | 20000 | x | + | 20000 | x | × | 1 | + | 20000 | x | x |
| = | 20000 | + | 20000 | x | + | 20000 | x | + | 20000 | x | x |
| = | 20000 | + | 40000 | x | + | 20000 | x | x |
| 20000 | + | 40000 | x | + | 20000 | x | x | = | 33800 |
| x2= | 3 10 |