| x | × | 1 | − | 2 | x | × | 2 | + | 6 | x | × | 3 | = | 0 |
| 方程左边 = | x | × | 1 | − | 4 | x | + | 18 | x |
| = | 15 | x |
| 15 | x | = | 0 |
| x | = | 0 | ÷ | 15 |
| = | 0 | × | 1 15 |
| x | = | 0 |
| 2 | x | × | 3 | = | 0 |
| 方程左边 = | 6 | x |
| 6 | x | = | 0 |
| x | = | 0 | ÷ | 6 |
| = | 0 | × | 1 6 |
| x | = | 0 |
| - | 2 | x | × | 1 | + | 4 | x | × | 2 | + | 12 | x | × | 3 | = | 0 |
| 方程左边 = | - | 2 | x | + | 8 | x | + | 36 | x |
| = | 42 | x |
| 42 | x | = | 0 |
| x | = | 0 | ÷ | 42 |
| = | 0 | × | 1 42 |
| x | = | 0 |