| ( | x | − | 5 | ) | ( | x | − | 6 | ) | ( | x | + | 7 | ) | = | 0 |
| 方程左边 = | x | ( | x | − | 6 | ) | ( | x | + | 7 | ) | − | 5 | ( | x | − | 6 | ) | ( | x | + | 7 | ) |
| = | x | x | ( | x | + | 7 | ) | − | x | × | 6 | ( | x | + | 7 | ) | − | 5 | ( | x | − | 6 | ) | ( | x | + | 7 | ) |
| = | x | x | x | + | x | x | × | 7 | − | x | × | 6 | ( | x | + | 7 | ) | − | 5 | ( | x | − | 6 | ) | ( | x | + | 7 | ) |
| = | x | x | x | + | x | x | × | 7 | − | x | × | 6 | x | − | x | × | 6 | × | 7 |
| = | x | x | x | + | x | x | × | 7 | − | x | × | 6 | x | − | x | × | 42 | − | 5 |
| = | x | x | x | + | x | x | × | 7 | − | x | × | 6 | x | − | 42 | x | − | 5 |
| = | x | x | x | + | x | x | × | 7 | − | x | × | 6 | x | − | 42 | x | − | 5 |
| = | x | x | x | + | x | x | × | 7 | − | x | × | 6 | x | − | 42 | x | − | 5 |
| = | x | x | x | + | x | x | × | 7 | − | x | × | 6 | x | − | 42 | x | − | 5 |
| = | x | x | x | + | x | x | × | 7 | − | x | × | 6 | x | − | 77 | x | − | 5 |
| = | x | x | x | + | x | x | × | 7 | − | x | × | 6 | x | − | 77 | x | − | 5 |
| = | x | x | x | + | x | x | × | 7 | − | x | × | 6 | x | − | 77 | x | − | 5 |
| = | x | x | x | + | x | x | × | 7 | − | x | × | 6 | x | − | 47 | x | − | 5 |
| x | x | x | + | x | x | × | 7 | − | x | × | 6 | x | − | 47 | x | − | 5 | = | 0 |