( | 18 | − | x | ) | ( | 200 | + | 30 | x | ) | = | 4480 |
方程左边 = | 18 | ( | 200 | + | 30 | x | ) | − | x | ( | 200 | + | 30 | x | ) |
= | 18 | × | 200 | + | 18 | × | 30 | x | − | x | ( | 200 | + | 30 | x | ) |
= | 3600 | + | 540 | x | − | x | ( | 200 | + | 30 | x | ) |
= | 3600 | + | 540 | x | − | x | × | 200 | − | x | × | 30 | x |
= | 3600 | + | 340 | x | − | x | × | 30 | x |
3600 | + | 340 | x | − | x | × | 30 | x | = | 4480 |
x2= | 22 3 |