( | 400 | + | 5 | x | ) | ( | 40 | − | 25 | − | x | ) | = | 4250 |
方程左边 = | 400 | ( | 40 | − | 25 | − | x | ) | + | 5 | x | ( | 40 | − | 25 | − | x | ) |
= | 400 | × | 40 | − | 400 | × | 25 | − | 400 | x | + | 5 | x | ( | 40 | − | 25 | − | x | ) |
= | 16000 | − | 10000 | − | 400 | x | + | 5 | x | ( | 40 | − | 25 | − | x | ) |
= | 6000 | − | 400 | x | + | 5 | x | ( | 40 | − | 25 | − | x | ) |
= | 6000 | − | 400 | x | + | 5 | x | × | 40 | − | 5 | x | × | 25 | − | 5 | x | x |
= | 6000 | − | 400 | x | + | 200 | x | − | 125 | x | − | 5 | x | x |
= | 6000 | − | 325 | x | − | 5 | x | x |
6000 | − | 325 | x | − | 5 | x | x | = | 4250 |