( | 360 | − | x | − | 280 | ) | ( | 5 | x | + | 60 | ) | = | 7200 |
方程左边 = | 360 | ( | 5 | x | + | 60 | ) | − | x | ( | 5 | x | + | 60 | ) | − | 280 | ( | 5 | x | + | 60 | ) |
= | 360 | × | 5 | x | + | 360 | × | 60 | − | x | ( | 5 | x | + | 60 | ) | − | 280 | ( | 5 | x | + | 60 | ) |
= | 1800 | x | + | 21600 | − | x | ( | 5 | x | + | 60 | ) | − | 280 | ( | 5 | x | + | 60 | ) |
= | 1800 | x | + | 21600 | − | x | × | 5 | x | − | x | × | 60 | − | 280 | ( | 5 | x | + | 60 | ) |
= | 1740 | x | + | 21600 | − | x | × | 5 | x | − | 280 | ( | 5 | x | + | 60 | ) |
= | 1740 | x | + | 21600 | − | x | × | 5 | x | − | 280 | × | 5 | x | − | 280 | × | 60 |
= | 1740 | x | + | 21600 | − | x | × | 5 | x | − | 1400 | x | − | 16800 |
= | 340 | x | + | 4800 | − | x | × | 5 | x |
340 | x | + | 4800 | − | x | × | 5 | x | = | 7200 |