| ( | x | − | 5 | ) | ( | 28 | − | 2 | ( | x | − | 10 | ) | ) | = | 0 |
| 方程左边 = | x | ( | 28 | − | 2 | ( | x | − | 10 | ) | ) | − | 5 | ( | 28 | − | 2 | ( | x | − | 10 | ) | ) |
| = | x | × | 28 | − | x | × | 2 | ( | x | − | 10 | ) | − | 5 | ( | 28 | − | 2 | ( | x | − | 10 | ) | ) |
| = | 28 | x | − | x | × | 2 | x | + | x | × | 2 | × | 10 | − | 5 | ( | 28 | − | 2 | ( | x | − | 10 | ) | ) |
| = | 28 | x | − | x | × | 2 | x | + | x | × | 20 | − | 5 | ( | 28 | − | 2 | ( | x | − | 10 | ) | ) |
| = | 48 | x | − | x | × | 2 | x | − | 5 | ( | 28 | − | 2 | ( | x | − | 10 | ) | ) |
| = | 48 | x | − | x | × | 2 | x | − | 5 | × | 28 | + | 5 | × | 2 | ( | x | − | 10 | ) |
| = | 48 | x | − | x | × | 2 | x | − | 140 | + | 10 | ( | x | − | 10 | ) |
| = | 48 | x | − | x | × | 2 | x | − | 140 | + | 10 | x | − | 10 | × | 10 |
| = | 48 | x | − | x | × | 2 | x | − | 140 | + | 10 | x | − | 100 |
| = | 58 | x | − | x | × | 2 | x | − | 240 |
| 58 | x | − | x | × | 2 | x | − | 240 | = | 0 |