| ( | 3 | x | − | 2 | ) | ( | 7 | − | 5 | x | ) | = | 0 |
| 方程左边 = | 3 | x | ( | 7 | − | 5 | x | ) | − | 2 | ( | 7 | − | 5 | x | ) |
| = | 3 | x | × | 7 | − | 3 | x | × | 5 | x | − | 2 | ( | 7 | − | 5 | x | ) |
| = | 21 | x | − | 15 | x | x | − | 2 | ( | 7 | − | 5 | x | ) |
| = | 21 | x | − | 15 | x | x | − | 2 | × | 7 | + | 2 | × | 5 | x |
| = | 21 | x | − | 15 | x | x | − | 14 | + | 10 | x |
| = | 31 | x | − | 15 | x | x | − | 14 |
| 31 | x | − | 15 | x | x | − | 14 | = | 0 |
| x1= | 2 3 |
| x2= | 7 5 |