| ( | - | 2 | x | + | 160 | ) | ( | x | − | 30 | ) | = | 1400 |
| Left side of the equation = | - | 2 | x | ( | x | − | 30 | ) | + | 160 | ( | x | − | 30 | ) |
| = | - | 2 | x | x | + | 2 | x | × | 30 | + | 160 | ( | x | − | 30 | ) |
| = | - | 2 | x | x | + | 60 | x | + | 160 | ( | x | − | 30 | ) |
| = | - | 2 | x | x | + | 60 | x | + | 160 | x | − | 160 | × | 30 |
| = | - | 2 | x | x | + | 60 | x | + | 160 | x | − | 4800 |
| = | - | 2 | x | x | + | 220 | x | − | 4800 |
| - | 2 | x | x | + | 220 | x | − | 4800 | = | 1400 |