| ( | x | − | 6 | ) | ( | - | 40 | x | + | 760 | ) | − | 300 | = | 0 |
| Left side of the equation = | x | ( | - | 40 | x | + | 760 | ) | − | 6 | ( | - | 40 | x | + | 760 | ) | − | 300 |
| = | - | x | × | 40 | x | + | x | × | 760 | − | 6 | ( | - | 40 | x | + | 760 | ) | − | 300 |
| = | - | x | × | 40 | x | + | 760 | x | + | 6 | × | 40 | x | − | 6 | × | 760 | − | 300 |
| = | - | x | × | 40 | x | + | 760 | x | + | 240 | x | − | 4560 | − | 300 |
| = | - | x | × | 40 | x | + | 1000 | x | − | 4860 |
| - | x | × | 40 | x | + | 1000 | x | − | 4860 | = | 0 |