| x | ( | 20 | − | x | ) | ( | 40 | − | x | ) | − | 114539 2 | = | 0 |
| Left side of the equation = | x | × | 20 | ( | 40 | − | x | ) | − | x | x | ( | 40 | − | x | ) | − | 114539 2 |
| = | x | × | 20 | × | 40 | − | x | × | 20 | x | − | x | x | ( | 40 | − | x | ) | − | 114539 2 |
| = | x | × | 800 | − | x | × | 20 | x | − | x | x | ( | 40 | − | x | ) | − | 114539 2 |
| = | 800 | x | − | x | × | 20 | x | − | x | x | × | 40 | + | x | x | x | − | 114539 2 |
| 800 | x | − | x | × | 20 | x | − | x | x | × | 40 | + | x | x | x | − | 114539 2 | = | 0 |