| 1 | ÷ | 2 | × | n | + | n | ( | n | − | 1 | ) | ÷ | 2 | × | ( | - | 1 | ÷ | 6 | ) | = | - | 5 |
| 方程左边 = | 1 2 | n | + | n | ( | n | − | 1 | ) | × | 1 2 | ( | - | 1 | ÷ | 6 | ) |
1 2 | n | + | n | ( | n | − | 1 | ) | × | 1 2 | ( | - | 1 | ÷ | 6 | ) | = | - | 5 |
| 方程左边 = | 1 2 | n | + | n | n | × | 1 2 | ( | - | 1 | ÷ | 6 | ) | − | n | × | 1 | × | 1 2 | ( | - | 1 | ÷ | 6 | ) |
| = | 1 2 | n | + | n | n | × | 1 2 | ( | - | 1 | ÷ | 6 | ) | − | n | × | 1 2 | ( | - | 1 | ÷ | 6 | ) |
| = | 1 2 | n | − | n | n | × | 1 2 | × | 1 | ÷ | 6 | − | n | × | 1 2 | ( | - | 1 | ÷ | 6 | ) |
| = | 1 2 | n | − | n | n | × | 1 12 | − | n | × | 1 2 | ( | - | 1 | ÷ | 6 | ) |
| = | 1 2 | n | − | n | n | × | 1 12 | + | n | × | 1 2 | × | 1 | ÷ | 6 |
| = | 1 2 | n | − | n | n | × | 1 12 | + | n | × | 1 12 |
| = | 7 12 | n | − | n | n | × | 1 12 |
7 12 | n | − | n | n | × | 1 12 | = | - | 5 |