| ( | n | − | 9 | ) | ( | n | − | 9 | ) | + | ( | n | − | 5 | ) | ( | n | − | 5 | ) | = | 9 |
| 方程左边 = | n | ( | n | − | 9 | ) | − | 9 | ( | n | − | 9 | ) | + | ( | n | − | 5 | ) | ( | n | − | 5 | ) |
| = | n | n | − | n | × | 9 | − | 9 | ( | n | − | 9 | ) | + | ( | n | − | 5 | ) | ( | n | − | 5 | ) |
| = | n | n | − | 9 | n | − | 9 | n | + | 9 | × | 9 | + | ( | n | − | 5 | ) | ( | n | − | 5 | ) |
| = | n | n | − | 9 | n | − | 9 | n | + | 81 | + | ( | n | − | 5 | ) | ( | n | − | 5 | ) |
| = | n | n | − | 18 | n | + | 81 | + | ( | n | − | 5 | ) | ( | n | − | 5 | ) |
| = | n | n | − | 18 | n | + | 81 | + | n | ( | n | − | 5 | ) | − | 5 | ( | n | − | 5 | ) |
| = | n | n | − | 18 | n | + | 81 | + | n | n | − | n | × | 5 | − | 5 | ( | n | − | 5 | ) |
| = | n | n | − | 23 | n | + | 81 | + | n | n | − | 5 | ( | n | − | 5 | ) |
| = | n | n | − | 23 | n | + | 81 | + | n | n | − | 5 | n | + | 5 | × | 5 |
| = | n | n | − | 23 | n | + | 81 | + | n | n | − | 5 | n | + | 25 |
| = | n | n | − | 28 | n | + | 106 | + | n | n |
| n | n | − | 28 | n | + | 106 | + | n | n | = | 9 |