| - | 15 16 | ( | x | + | 4 | ) | ( | x | + | 4 | ) | + | 18 | = | 0 |
| Left side of the equation = | - | 15 16 | x | ( | x | + | 4 | ) | − | 15 16 | × | 4 | ( | x | + | 4 | ) | + | 18 |
| = | - | 15 16 | x | ( | x | + | 4 | ) | − | 15 4 | ( | x | + | 4 | ) | + | 18 |
| = | - | 15 16 | x | x | − | 15 16 | x | × | 4 | − | 15 4 | ( | x | + | 4 | ) | + | 18 |
| = | - | 15 16 | x | x | − | 15 4 | x | − | 15 4 | ( | x | + | 4 | ) | + | 18 |
| = | - | 15 16 | x | x | − | 15 4 | x | − | 15 4 | x | − | 15 4 | × | 4 | + | 18 |
| = | - | 15 16 | x | x | − | 15 4 | x | − | 15 4 | x | − | 15 | + | 18 |
| = | - | 15 16 | x | x | − | 15 2 | x | + | 3 |
| - | 15 16 | x | x | − | 15 2 | x | + | 3 | = | 0 |