| ( | x | − | 5 | ) | ( | 5 2 | x | − | 25 2 | ) | = | 20 | x |
| Left side of the equation = | x | ( | 5 2 | x | − | 25 2 | ) | − | 5 | ( | 5 2 | x | − | 25 2 | ) |
| = | x | × | 5 2 | x | − | x | × | 25 2 | − | 5 | ( | 5 2 | x | − | 25 2 | ) |
| = | x | × | 5 2 | x | − | 25 2 | x | − | 5 | × | 5 2 | x | + | 5 | × | 25 2 |
| = | x | × | 5 2 | x | − | 25 2 | x | − | 25 2 | x | + | 125 2 |
| = | x | × | 5 2 | x | − | 25 | x | + | 125 2 |
| x | × | 5 2 | x | − | 25 | x | + | 125 2 | = | 20 | x |