| ( | 400 | − | 10 | x | ) | ( | 60 | − | 1 2 | x | ) | − | 40 | x | − | 1600 | + | 1175 | = | 0 |
| 方程左边 = | ( | 400 | − | 10 | x | ) | ( | 60 | − | 1 2 | x | ) | − | 40 | x | − | 425 |
| ( | 400 | − | 10 | x | ) | ( | 60 | − | 1 2 | x | ) | − | 40 | x | − | 425 | = | 0 |
| 方程左边 = | 400 | ( | 60 | − | 1 2 | x | ) | − | 10 | x | ( | 60 | − | 1 2 | x | ) | − | 40 | x | − | 425 |
| = | 400 | × | 60 | − | 400 | × | 1 2 | x | − | 10 | x | ( | 60 | − | 1 2 | x | ) | − | 40 | x | − | 425 |
| = | 24000 | − | 200 | x | − | 10 | x | ( | 60 | − | 1 2 | x | ) | − | 40 | x | − | 425 |
| = | 23575 | − | 240 | x | − | 10 | x | ( | 60 | − | 1 2 | x | ) |
| = | 23575 | − | 240 | x | − | 10 | x | × | 60 | + | 10 | x | × | 1 2 | x |
| = | 23575 | − | 240 | x | − | 600 | x | + | 5 | x | x |
| = | 23575 | − | 840 | x | + | 5 | x | x |
| 23575 | − | 840 | x | + | 5 | x | x | = | 0 |