( | 200 | + | 20 | ( | 60 | − | x | ) | ) | ( | x | − | 40 | ) | = | 0 |
方程左边 = | 200 | ( | x | − | 40 | ) | + | 20 | ( | 60 | − | x | ) | ( | x | − | 40 | ) |
= | 200 | x | − | 200 | × | 40 | + | 20 | ( | 60 | − | x | ) | ( | x | − | 40 | ) |
= | 200 | x | − | 8000 | + | 20 | ( | 60 | − | x | ) | ( | x | − | 40 | ) |
= | 200 | x | − | 8000 | + | 20 | × | 60 | ( | x | − | 40 | ) | − | 20 | x | ( | x | − | 40 | ) |
= | 200 | x | − | 8000 | + | 1200 | ( | x | − | 40 | ) | − | 20 | x | ( | x | − | 40 | ) |
= | 200 | x | − | 8000 | + | 1200 | x | − | 1200 | × | 40 | − | 20 | x | ( | x | − | 40 | ) |
= | 200 | x | − | 8000 | + | 1200 | x | − | 48000 | − | 20 | x | ( | x | − | 40 | ) |
= | 1400 | x | − | 56000 | − | 20 | x | ( | x | − | 40 | ) |
= | 1400 | x | − | 56000 | − | 20 | x | x | + | 20 | x | × | 40 |
= | 1400 | x | − | 56000 | − | 20 | x | x | + | 800 | x |
= | 2200 | x | − | 56000 | − | 20 | x | x |
2200 | x | − | 56000 | − | 20 | x | x | = | 0 |