( | 200 | + | 10 | x | ) | ( | 64 | − | x | ) | = | 14400 |
方程左边 = | 200 | ( | 64 | − | x | ) | + | 10 | x | ( | 64 | − | x | ) |
= | 200 | × | 64 | − | 200 | x | + | 10 | x | ( | 64 | − | x | ) |
= | 12800 | − | 200 | x | + | 10 | x | ( | 64 | − | x | ) |
= | 12800 | − | 200 | x | + | 10 | x | × | 64 | − | 10 | x | x |
= | 12800 | − | 200 | x | + | 640 | x | − | 10 | x | x |
= | 12800 | + | 440 | x | − | 10 | x | x |
12800 | + | 440 | x | − | 10 | x | x | = | 14400 |