| 10 | ( | 2 | x | + | 3 | ) | + | x | = | 10 | + | x | ( | 2 | x | + | 3 | ) | + | 5 |
| 方程左边 = | 10 | × | 2 | x | + | 10 | × | 3 | + | x |
| = | 20 | x | + | 30 | + | x |
| = | 21 | x | + | 30 |
| 21 | x | + | 30 | = | 10 | + | x | ( | 2 | x | + | 3 | ) | + | 5 |
| 方程右边 = | 15 | + | x | ( | 2 | x | + | 3 | ) |
| 21 | x | + | 30 | = | 15 | + | x | ( | 2 | x | + | 3 | ) |
| 方程右边 = | 15 | + | x | × | 2 | x | + | x | × | 3 |
| 21 | x | + | 30 | = | 15 | + | x | × | 2 | x | + | 3 | x |