| ( | m | − | 2 | ) | ÷ | 2 | × | ( | - | m | − | 4 | ) | = | - | 4 |
| 方程左边 = | m | × | 1 2 | ( | - | m | − | 4 | ) | − | 2 | × | 1 2 | ( | - | m | − | 4 | ) |
| = | m | × | 1 2 | ( | - | m | − | 4 | ) | − | 1 | ( | - | m | − | 4 | ) |
| = | - | m | × | 1 2 | m | − | m | × | 1 2 | × | 4 | − | 1 | ( | - | m | − | 4 | ) |
| = | - | m | × | 1 2 | m | − | m | × | 2 | − | 1 | ( | - | m | − | 4 | ) |
| = | - | m | × | 1 2 | m | − | 2 | m | + | 1 | m | + | 1 | × | 4 |
| = | - | m | × | 1 2 | m | − | 2 | m | + | 1 | m | + | 4 |
| = | - | m | × | 1 2 | m | − | 1 | m | + | 4 |
| - | m | × | 1 2 | m | − | 1 | m | + | 4 | = | - | 4 |