| ( | x | − | 100 | ) | ( | x | − | 98 | ) | = | 99 | × | 99 |
| Left side of the equation = | x | ( | x | − | 98 | ) | − | 100 | ( | x | − | 98 | ) |
| = | x | x | − | x | × | 98 | − | 100 | ( | x | − | 98 | ) |
| = | x | x | − | 98 | x | − | 100 | x | + | 100 | × | 98 |
| = | x | x | − | 98 | x | − | 100 | x | + | 9800 |
| = | x | x | − | 198 | x | + | 9800 |
| x | x | − | 198 | x | + | 9800 | = | 99 | × | 99 |
| Right side of the equation = | 9801 |
| x | x | − | 198 | x | + | 9800 | = | 9801 |