| ( | 441 | − | a | ) | ( | a | − | 81 | ) | = | ( | 225 | − | a | ) | ( | a | − | 9 | ) |
| Left side of the equation = | 441 | ( | a | − | 81 | ) | − | a | ( | a | − | 81 | ) |
| = | 441 | a | − | 441 | × | 81 | − | a | ( | a | − | 81 | ) |
| = | 441 | a | − | 35721 | − | a | ( | a | − | 81 | ) |
| = | 441 | a | − | 35721 | − | a | a | + | a | × | 81 |
| = | 522 | a | − | 35721 | − | a | a |
| 522 | a | − | 35721 | − | a | a | = | ( | 225 | − | a | ) | ( | a | − | 9 | ) |
| Right side of the equation = | 225 | ( | a | − | 9 | ) | − | a | ( | a | − | 9 | ) |
| = | 225 | a | − | 225 | × | 9 | − | a | ( | a | − | 9 | ) |
| = | 225 | a | − | 2025 | − | a | ( | a | − | 9 | ) |
| = | 225 | a | − | 2025 | − | a | a | + | a | × | 9 |
| = | 234 | a | − | 2025 | − | a | a |
| 522 | a | − | 35721 | − | a | a | = | 234 | a | − | 2025 | − | a | a |