| ( | x | − | 100 | ) | ( | - | 2 | x | + | 320 | ) | = | 0 |
| Left side of the equation = | x | ( | - | 2 | x | + | 320 | ) | − | 100 | ( | - | 2 | x | + | 320 | ) |
| = | - | x | × | 2 | x | + | x | × | 320 | − | 100 | ( | - | 2 | x | + | 320 | ) |
| = | - | x | × | 2 | x | + | 320 | x | + | 100 | × | 2 | x | − | 100 | × | 320 |
| = | - | x | × | 2 | x | + | 320 | x | + | 200 | x | − | 32000 |
| = | - | x | × | 2 | x | + | 520 | x | − | 32000 |
| - | x | × | 2 | x | + | 520 | x | − | 32000 | = | 0 |