150 | x | ( | x | − | 25 | ) | + | 200 | x | ( | x | − | 20 | ) | = | 3800 |
方程左边 = | 150 | x | x | − | 150 | x | × | 25 | + | 200 | x | ( | x | − | 20 | ) |
= | 150 | x | x | − | 3750 | x | + | 200 | x | ( | x | − | 20 | ) |
= | 150 | x | x | − | 3750 | x | + | 200 | x | x | − | 200 | x | × | 20 |
= | 150 | x | x | − | 3750 | x | + | 200 | x | x | − | 4000 | x |
= | 150 | x | x | − | 7750 | x | + | 200 | x | x |
150 | x | x | − | 7750 | x | + | 200 | x | x | = | 3800 |