( | x | − | 40 | ) | ( | - | 2 | x | + | 200 | ) | = | 1600 |
方程左边 = | x | ( | - | 2 | x | + | 200 | ) | − | 40 | ( | - | 2 | x | + | 200 | ) |
= | - | x | × | 2 | x | + | x | × | 200 | − | 40 | ( | - | 2 | x | + | 200 | ) |
= | - | x | × | 2 | x | + | 200 | x | + | 40 | × | 2 | x | − | 40 | × | 200 |
= | - | x | × | 2 | x | + | 200 | x | + | 80 | x | − | 8000 |
= | - | x | × | 2 | x | + | 280 | x | − | 8000 |
- | x | × | 2 | x | + | 280 | x | − | 8000 | = | 1600 |