| ( | 25 | − | x | ) | ( | 25 | − | x | ) | + | ( | x | − | 10 | ) | ( | x | − | 10 | ) | = | 1 |
| Left side of the equation = | 25 | ( | 25 | − | x | ) | − | x | ( | 25 | − | x | ) | + | ( | x | − | 10 | ) | ( | x | − | 10 | ) |
| = | 25 | × | 25 | − | 25 | x | − | x | ( | 25 | − | x | ) | + | ( | x | − | 10 | ) | ( | x | − | 10 | ) |
| = | 625 | − | 25 | x | − | x | ( | 25 | − | x | ) | + | ( | x | − | 10 | ) | ( | x | − | 10 | ) |
| = | 625 | − | 25 | x | − | x | × | 25 | + | x | x | + | ( | x | − | 10 | ) | ( | x | − | 10 | ) |
| = | 625 | − | 50 | x | + | x | x | + | ( | x | − | 10 | ) | ( | x | − | 10 | ) |
| = | 625 | − | 50 | x | + | x | x | + | x | ( | x | − | 10 | ) | − | 10 | ( | x | − | 10 | ) |
| = | 625 | − | 50 | x | + | x | x | + | x | x | − | x | × | 10 | − | 10 | ( | x | − | 10 | ) |
| = | 625 | − | 60 | x | + | x | x | + | x | x | − | 10 | ( | x | − | 10 | ) |
| = | 625 | − | 60 | x | + | x | x | + | x | x | − | 10 | x | + | 10 | × | 10 |
| = | 625 | − | 60 | x | + | x | x | + | x | x | − | 10 | x | + | 100 |
| = | 725 | − | 70 | x | + | x | x | + | x | x |
| 725 | − | 70 | x | + | x | x | + | x | x | = | 1 |