| ( | x | + | 3 | ) | ( | - | 1 2 | x | + | 4 | ) | = | 15 |
| Left side of the equation = | x | ( | - | 1 2 | x | + | 4 | ) | + | 3 | ( | - | 1 2 | x | + | 4 | ) |
| = | - | x | × | 1 2 | x | + | x | × | 4 | + | 3 | ( | - | 1 2 | x | + | 4 | ) |
| = | - | x | × | 1 2 | x | + | 4 | x | − | 3 | × | 1 2 | x | + | 3 | × | 4 |
| = | - | x | × | 1 2 | x | + | 4 | x | − | 3 2 | x | + | 12 |
| = | - | x | × | 1 2 | x | + | 5 2 | x | + | 12 |
| - | x | × | 1 2 | x | + | 5 2 | x | + | 12 | = | 15 |