| ( | x | − | 100 | ) | ( | 1300 | − | 5 | x | ) | = | 0 |
| 方程左边 = | x | ( | 1300 | − | 5 | x | ) | − | 100 | ( | 1300 | − | 5 | x | ) |
| = | x | × | 1300 | − | x | × | 5 | x | − | 100 | ( | 1300 | − | 5 | x | ) |
| = | 1300 | x | − | x | × | 5 | x | − | 100 | × | 1300 | + | 100 | × | 5 | x |
| = | 1300 | x | − | x | × | 5 | x | − | 130000 | + | 500 | x |
| = | 1800 | x | − | x | × | 5 | x | − | 130000 |
| 1800 | x | − | x | × | 5 | x | − | 130000 | = | 0 |