| ( | 173 10 | − | x | ) | ( | 10 | + | x | ) | = | 173 |
| Left side of the equation = | 173 10 | ( | 10 | + | x | ) | − | x | ( | 10 | + | x | ) |
| = | 173 10 | × | 10 | + | 173 10 | x | − | x | ( | 10 | + | x | ) |
| = | 173 | + | 173 10 | x | − | x | ( | 10 | + | x | ) |
| = | 173 | + | 173 10 | x | − | x | × | 10 | − | x | x |
| = | 173 | + | 73 10 | x | − | x | x |
| 173 | + | 73 10 | x | − | x | x | = | 173 |
| x2= | 73 10 |