| ( | x | − | 1 | ) | ( | x | − | 20 | ) | ( | x | − | 20 | ) | = | 144 |
| Left side of the equation = | x | ( | x | − | 20 | ) | ( | x | − | 20 | ) | − | 1 | ( | x | − | 20 | ) | ( | x | − | 20 | ) |
| = | x | x | ( | x | − | 20 | ) | − | x | × | 20 | ( | x | − | 20 | ) | − | 1 | ( | x | − | 20 | ) | ( | x | − | 20 | ) |
| = | x | x | x | − | x | x | × | 20 | − | x | × | 20 | ( | x | − | 20 | ) | − | 1 | ( | x | − | 20 | ) | ( | x | − | 20 | ) |
| = | x | x | x | − | x | x | × | 20 | − | x | × | 20 | x | + | x | × | 20 | × | 20 |
| = | x | x | x | − | x | x | × | 20 | − | x | × | 20 | x | + | x | × | 400 | − | 1 |
| = | x | x | x | − | x | x | × | 20 | − | x | × | 20 | x | + | 400 | x | − | 1 |
| = | x | x | x | − | x | x | × | 20 | − | x | × | 20 | x | + | 400 | x | − | 1 |
| = | x | x | x | − | x | x | × | 20 | − | x | × | 20 | x | + | 400 | x | − | 1 |
| = | x | x | x | − | x | x | × | 20 | − | x | × | 20 | x | + | 400 | x | − | 1 |
| = | x | x | x | − | x | x | × | 20 | − | x | × | 20 | x | + | 420 | x | − | 1 |
| = | x | x | x | − | x | x | × | 20 | − | x | × | 20 | x | + | 420 | x | − | 1 |
| = | x | x | x | − | x | x | × | 20 | − | x | × | 20 | x | + | 420 | x | − | 1 |
| = | x | x | x | − | x | x | × | 20 | − | x | × | 20 | x | + | 440 | x | − | 1 |
| x | x | x | − | x | x | × | 20 | − | x | × | 20 | x | + | 440 | x | − | 1 | = | 144 |
| x1=17 |