( | X | − | 100 | ) | ( | 3400 | − | 20 | X | ) | = | 24000 |
方程左边 = | X | ( | 3400 | − | 20 | X | ) | − | 100 | ( | 3400 | − | 20 | X | ) |
= | X | × | 3400 | − | X | × | 20 | X | − | 100 | ( | 3400 | − | 20 | X | ) |
= | 3400 | X | − | X | × | 20 | X | − | 100 | × | 3400 | + | 100 | × | 20 | X |
= | 3400 | X | − | X | × | 20 | X | − | 340000 | + | 2000 | X |
= | 5400 | X | − | X | × | 20 | X | − | 340000 |
5400 | X | − | X | × | 20 | X | − | 340000 | = | 24000 |