| x | x | − | ( | x | − | 30 | ) | ( | x | − | 30 | ) | = | 3600 |
| Left side of the equation = | x | x | − | x | ( | x | − | 30 | ) | + | 30 | ( | x | − | 30 | ) |
| = | x | x | − | x | x | + | x | × | 30 | + | 30 | ( | x | − | 30 | ) |
| = | x | x | − | x | x | + | 30 | x | + | 30 | x | − | 30 | × | 30 |
| = | x | x | − | x | x | + | 30 | x | + | 30 | x | − | 900 |
| = | x | x | − | x | x | + | 60 | x | − | 900 |
| x | x | − | x | x | + | 60 | x | − | 900 | = | 3600 |