| - | 3 | x | − | ( | 1 | + | x | ) | ( | x | − | 4 | ) | = | 0 |
| Left side of the equation = | - | 3 | x | − | 1 | ( | x | − | 4 | ) | − | x | ( | x | − | 4 | ) |
| = | - | 3 | x | − | 1 | x | + | 1 | × | 4 | − | x | ( | x | − | 4 | ) |
| = | - | 3 | x | − | 1 | x | + | 4 | − | x | ( | x | − | 4 | ) |
| = | - | 4 | x | + | 4 | − | x | ( | x | − | 4 | ) |
| = | - | 4 | x | + | 4 | − | x | x | + | x | × | 4 |
| = | - | 0 | x | + | 4 | − | x | x |
| - | 0 | x | + | 4 | − | x | x | = | 0 |