| ( | 1 10 | − | x | + | 9 | ) | ( | x | − | 40 | ) | = | 168 5 |
| 方程左边 = | 1 10 | ( | x | − | 40 | ) | − | x | ( | x | − | 40 | ) | + | 9 | ( | x | − | 40 | ) |
| = | 1 10 | x | − | 1 10 | × | 40 | − | x | ( | x | − | 40 | ) | + | 9 | ( | x | − | 40 | ) |
| = | 1 10 | x | − | 4 | − | x | ( | x | − | 40 | ) | + | 9 | ( | x | − | 40 | ) |
| = | 1 10 | x | − | 4 | − | x | x | + | x | × | 40 | + | 9 | ( | x | − | 40 | ) |
| = | 401 10 | x | − | 4 | − | x | x | + | 9 | ( | x | − | 40 | ) |
| = | 401 10 | x | − | 4 | − | x | x | + | 9 | x | − | 9 | × | 40 |
| = | 401 10 | x | − | 4 | − | x | x | + | 9 | x | − | 360 |
| = | 491 10 | x | − | 364 | − | x | x |
491 10 | x | − | 364 | − | x | x | = | 168 5 |