| x | ( | 9 | − | x | ) | = | ( | 1 | − | x | ) | ( | 8 | − | x | ) |
| Left side of the equation = | x | × | 9 | − | x | x |
| 9 | x | − | x | x | = | ( | 1 | − | x | ) | ( | 8 | − | x | ) |
| Right side of the equation = | 1 | ( | 8 | − | x | ) | − | x | ( | 8 | − | x | ) |
| = | 1 | × | 8 | − | 1 | x | − | x | ( | 8 | − | x | ) |
| = | 8 | − | 1 | x | − | x | ( | 8 | − | x | ) |
| = | 8 | − | 1 | x | − | x | × | 8 | + | x | x |
| = | 8 | − | 9 | x | + | x | x |
| 9 | x | − | x | x | = | 8 | − | 9 | x | + | x | x |