( | 40 | − | 1 2 | x | ) | ( | 30 | + | 4 | x | ) | = | 510 |
方程左边 = | 40 | ( | 30 | + | 4 | x | ) | − | 1 2 | x | ( | 30 | + | 4 | x | ) |
= | 40 | × | 30 | + | 40 | × | 4 | x | − | 1 2 | x | ( | 30 | + | 4 | x | ) |
= | 1200 | + | 160 | x | − | 1 2 | x | ( | 30 | + | 4 | x | ) |
= | 1200 | + | 160 | x | − | 1 2 | x | × | 30 | − | 1 2 | x | × | 4 | x |
= | 1200 | + | 160 | x | − | 15 | x | − | 2 | x | x |
= | 1200 | + | 145 | x | − | 2 | x | x |
1200 | + | 145 | x | − | 2 | x | x | = | 510 |