| x | ( | 9 | − | x | ) | = | ( | 10 | ( | 9 | − | x | ) | + | x | ) | × | 1 2 |
| Left side of the equation = | x | × | 9 | − | x | x |
| 9 | x | − | x | x | = | ( | 10 | ( | 9 | − | x | ) | + | x | ) | × | 1 2 |
| Right side of the equation = | 10 | ( | 9 | − | x | ) | × | 1 2 | + | x | × | 1 2 |
| = | 5 | ( | 9 | − | x | ) | + | x | × | 1 2 |
| = | 5 | × | 9 | − | 5 | x | + | 1 2 | x |
| = | 45 | − | 5 | x | + | 1 2 | x |
| = | 45 | − | 9 2 | x |
| 9 | x | − | x | x | = | 45 | − | 9 2 | x |
| x2= | 15 2 |