| ( | 50 | − | 9 | x | ) | ( | 9 | x | + | 5 | ) | = | 736 |
| 方程左边 = | 50 | ( | 9 | x | + | 5 | ) | − | 9 | x | ( | 9 | x | + | 5 | ) |
| = | 50 | × | 9 | x | + | 50 | × | 5 | − | 9 | x | ( | 9 | x | + | 5 | ) |
| = | 450 | x | + | 250 | − | 9 | x | ( | 9 | x | + | 5 | ) |
| = | 450 | x | + | 250 | − | 9 | x | × | 9 | x | − | 9 | x | × | 5 |
| = | 450 | x | + | 250 | − | 81 | x | x | − | 45 | x |
| = | 405 | x | + | 250 | − | 81 | x | x |
| 405 | x | + | 250 | − | 81 | x | x | = | 736 |