| 3 | ( | x | − | 5 | ) | ( | x | + | 15 | ) | = | 6 | ( | - | 5 | x | − | 3 | ) | ( | 9 | x | + | 2 | ) |
| Left side of the equation = | 3 | x | ( | x | + | 15 | ) | − | 3 | × | 5 | ( | x | + | 15 | ) |
| = | 3 | x | ( | x | + | 15 | ) | − | 15 | ( | x | + | 15 | ) |
| = | 3 | x | x | + | 3 | x | × | 15 | − | 15 | ( | x | + | 15 | ) |
| = | 3 | x | x | + | 45 | x | − | 15 | ( | x | + | 15 | ) |
| = | 3 | x | x | + | 45 | x | − | 15 | x | − | 15 | × | 15 |
| = | 3 | x | x | + | 45 | x | − | 15 | x | − | 225 |
| = | 3 | x | x | + | 30 | x | − | 225 |
| 3 | x | x | + | 30 | x | − | 225 | = | 6 | ( | - | 5 | x | − | 3 | ) | ( | 9 | x | + | 2 | ) |
| Right side of the equation = | - | 6 | × | 5 | x | ( | 9 | x | + | 2 | ) | − | 6 | × | 3 | ( | 9 | x | + | 2 | ) |
| = | - | 30 | x | ( | 9 | x | + | 2 | ) | − | 18 | ( | 9 | x | + | 2 | ) |
| = | - | 30 | x | × | 9 | x | − | 30 | x | × | 2 | − | 18 | ( | 9 | x | + | 2 | ) |
| = | - | 270 | x | x | − | 60 | x | − | 18 | ( | 9 | x | + | 2 | ) |
| = | - | 270 | x | x | − | 60 | x | − | 18 | × | 9 | x | − | 18 | × | 2 |
| = | - | 270 | x | x | − | 60 | x | − | 162 | x | − | 36 |
| = | - | 270 | x | x | − | 222 | x | − | 36 |
| 3 | x | x | + | 30 | x | − | 225 | = | - | 270 | x | x | − | 222 | x | − | 36 |