( | 1 2 | − | 1 5 | x | ) | ( | 600 | + | 1500 | x | ) | = | 300 |
方程左边 = | 1 2 | ( | 600 | + | 1500 | x | ) | − | 1 5 | x | ( | 600 | + | 1500 | x | ) |
= | 1 2 | × | 600 | + | 1 2 | × | 1500 | x | − | 1 5 | x | ( | 600 | + | 1500 | x | ) |
= | 300 | + | 750 | x | − | 1 5 | x | ( | 600 | + | 1500 | x | ) |
= | 300 | + | 750 | x | − | 1 5 | x | × | 600 | − | 1 5 | x | × | 1500 | x |
= | 300 | + | 750 | x | − | 120 | x | − | 300 | x | x |
= | 300 | + | 630 | x | − | 300 | x | x |
300 | + | 630 | x | − | 300 | x | x | = | 300 |
x2= | 21 10 |