( | x | − | 30 | ) | ( | - | 2 | x | + | 160 | ) | = | 800 |
方程左边 = | x | ( | - | 2 | x | + | 160 | ) | − | 30 | ( | - | 2 | x | + | 160 | ) |
= | - | x | × | 2 | x | + | x | × | 160 | − | 30 | ( | - | 2 | x | + | 160 | ) |
= | - | x | × | 2 | x | + | 160 | x | + | 30 | × | 2 | x | − | 30 | × | 160 |
= | - | x | × | 2 | x | + | 160 | x | + | 60 | x | − | 4800 |
= | - | x | × | 2 | x | + | 220 | x | − | 4800 |
- | x | × | 2 | x | + | 220 | x | − | 4800 | = | 800 |