w | = | ( | 7 | − | 4 | ) | ( | - | 50 | × | 7 | + | 1200 | ) |
方程右边 = | 7 | ( | - | 50 | × | 7 | + | 1200 | ) | − | 4 | ( | - | 50 | × | 7 | + | 1200 | ) |
= | - | 7 | × | 50 | × | 7 | + | 7 | × | 1200 | − | 4 | ( | - | 50 | × | 7 | + | 1200 | ) |
= | - | 2450 | + | 8400 | − | 4 | ( | - | 50 | × | 7 | + | 1200 | ) |
= | 5950 | − | 4 | ( | - | 50 | × | 7 | + | 1200 | ) |
= | 5950 | + | 4 | × | 50 | × | 7 | − | 4 | × | 1200 |
= | 5950 | + | 1400 | − | 4800 |
= | 2550 |
w | = | 2550 |