| 600 | = | - | 2 | ( | x | − | 90 | ) | ( | x | − | 50 | ) |
| Right side of the equation = | - | 2 | x | ( | x | − | 50 | ) | + | 2 | × | 90 | ( | x | − | 50 | ) |
| = | - | 2 | x | ( | x | − | 50 | ) | + | 180 | ( | x | − | 50 | ) |
| = | - | 2 | x | x | + | 2 | x | × | 50 | + | 180 | ( | x | − | 50 | ) |
| = | - | 2 | x | x | + | 100 | x | + | 180 | ( | x | − | 50 | ) |
| = | - | 2 | x | x | + | 100 | x | + | 180 | x | − | 180 | × | 50 |
| = | - | 2 | x | x | + | 100 | x | + | 180 | x | − | 9000 |
| = | - | 2 | x | x | + | 280 | x | − | 9000 |
| 600 | = | - | 2 | x | x | + | 280 | x | − | 9000 |