| ( | x | − | 10 | ) | ( | - | 100 | x | + | 2400 | ) | + | 40 | ( | x | − | 10 | − | 2 | ) | = | 0 |
| 方程左边 = | x | ( | - | 100 | x | + | 2400 | ) | − | 10 | ( | - | 100 | x | + | 2400 | ) | + | 40 | ( | x | − | 10 | − | 2 | ) |
| = | - | x | × | 100 | x | + | x | × | 2400 | − | 10 | ( | - | 100 | x | + | 2400 | ) | + | 40 | ( | x | − | 10 | − | 2 | ) |
| = | - | x | × | 100 | x | + | 2400 | x | + | 10 | × | 100 | x | − | 10 | × | 2400 | + | 40 | ( | x | − | 10 | − | 2 | ) |
| = | - | x | × | 100 | x | + | 2400 | x | + | 1000 | x | − | 24000 | + | 40 | ( | x | − | 10 | − | 2 | ) |
| = | - | x | × | 100 | x | + | 3400 | x | − | 24000 | + | 40 | ( | x | − | 10 | − | 2 | ) |
| = | - | x | × | 100 | x | + | 3400 | x | − | 24000 | + | 40 | x | − | 40 | × | 10 | − | 40 | × | 2 |
| = | - | x | × | 100 | x | + | 3400 | x | − | 24000 | + | 40 | x | − | 400 | − | 80 |
| = | - | x | × | 100 | x | + | 3440 | x | − | 24480 |
| - | x | × | 100 | x | + | 3440 | x | − | 24480 | = | 0 |