( | 100 | − | x | ) | × | 2 | ( | 60 | − | x | ) | = | 1000 | + | 8000 |
方程左边 = | 100 | × | 2 | ( | 60 | − | x | ) | − | x | × | 2 | ( | 60 | − | x | ) |
= | 200 | ( | 60 | − | x | ) | − | x | × | 2 | ( | 60 | − | x | ) |
= | 200 | × | 60 | − | 200 | x | − | x | × | 2 | ( | 60 | − | x | ) |
= | 12000 | − | 200 | x | − | x | × | 2 | ( | 60 | − | x | ) |
= | 12000 | − | 200 | x | − | x | × | 2 | × | 60 | + | x | × | 2 | x |
= | 12000 | − | 200 | x | − | x | × | 120 | + | x | × | 2 | x |
= | 12000 | − | 320 | x | + | x | × | 2 | x |
12000 | − | 320 | x | + | x | × | 2 | x | = | 1000 | + | 8000 |
方程右边 = | 9000 |
12000 | − | 320 | x | + | x | × | 2 | x | = | 9000 |