| ( | x | − | 1000 | ) | ( | 2000 | − | x | ) | = | 210000 |
| Left side of the equation = | x | ( | 2000 | − | x | ) | − | 1000 | ( | 2000 | − | x | ) |
| = | x | × | 2000 | − | x | x | − | 1000 | ( | 2000 | − | x | ) |
| = | 2000 | x | − | x | x | − | 1000 | × | 2000 | + | 1000 | x |
| = | 2000 | x | − | x | x | − | 2000000 | + | 1000 | x |
| = | 3000 | x | − | x | x | − | 2000000 |
| 3000 | x | − | x | x | − | 2000000 | = | 210000 |