| ( | 3 | x | + | 5 | ) | ( | 2 | x | − | 5 | ) | = | 3 | x | + | 5 |
| 方程左边 = | 3 | x | ( | 2 | x | − | 5 | ) | + | 5 | ( | 2 | x | − | 5 | ) |
| = | 3 | x | × | 2 | x | − | 3 | x | × | 5 | + | 5 | ( | 2 | x | − | 5 | ) |
| = | 6 | x | x | − | 15 | x | + | 5 | ( | 2 | x | − | 5 | ) |
| = | 6 | x | x | − | 15 | x | + | 5 | × | 2 | x | − | 5 | × | 5 |
| = | 6 | x | x | − | 15 | x | + | 10 | x | − | 25 |
| = | 6 | x | x | − | 5 | x | − | 25 |
| 6 | x | x | − | 5 | x | − | 25 | = | 3 | x | + | 5 |
| x1= | - | 5 3 |
| x2=3 |