| ( | x | − | 30 | ) | ( | 2 | x | − | 80 | ) | = | 2450 |
| Left side of the equation = | x | ( | 2 | x | − | 80 | ) | − | 30 | ( | 2 | x | − | 80 | ) |
| = | x | × | 2 | x | − | x | × | 80 | − | 30 | ( | 2 | x | − | 80 | ) |
| = | x | × | 2 | x | − | 80 | x | − | 30 | × | 2 | x | + | 30 | × | 80 |
| = | x | × | 2 | x | − | 80 | x | − | 60 | x | + | 2400 |
| = | x | × | 2 | x | − | 140 | x | + | 2400 |
| x | × | 2 | x | − | 140 | x | + | 2400 | = | 2450 |