( | 58 | − | 35 | − | x | ) | ( | 400 | + | 20 | x | ) | = | 8400 |
方程左边 = | 58 | ( | 400 | + | 20 | x | ) | − | 35 | ( | 400 | + | 20 | x | ) | − | x | ( | 400 | + | 20 | x | ) |
= | 58 | × | 400 | + | 58 | × | 20 | x | − | 35 | ( | 400 | + | 20 | x | ) | − | x | ( | 400 | + | 20 | x | ) |
= | 23200 | + | 1160 | x | − | 35 | ( | 400 | + | 20 | x | ) | − | x | ( | 400 | + | 20 | x | ) |
= | 23200 | + | 1160 | x | − | 35 | × | 400 | − | 35 | × | 20 | x | − | x | ( | 400 | + | 20 | x | ) |
= | 23200 | + | 1160 | x | − | 14000 | − | 700 | x | − | x | ( | 400 | + | 20 | x | ) |
= | 9200 | + | 460 | x | − | x | ( | 400 | + | 20 | x | ) |
= | 9200 | + | 460 | x | − | x | × | 400 | − | x | × | 20 | x |
= | 9200 | + | 60 | x | − | x | × | 20 | x |
9200 | + | 60 | x | − | x | × | 20 | x | = | 8400 |