( | 52 | − | 2 | x | ) | ( | 28 | − | 2 | x | ) | = | 640 |
方程左边 = | 52 | ( | 28 | − | 2 | x | ) | − | 2 | x | ( | 28 | − | 2 | x | ) |
= | 52 | × | 28 | − | 52 | × | 2 | x | − | 2 | x | ( | 28 | − | 2 | x | ) |
= | 1456 | − | 104 | x | − | 2 | x | ( | 28 | − | 2 | x | ) |
= | 1456 | − | 104 | x | − | 2 | x | × | 28 | + | 2 | x | × | 2 | x |
= | 1456 | − | 104 | x | − | 56 | x | + | 4 | x | x |
= | 1456 | − | 160 | x | + | 4 | x | x |
1456 | − | 160 | x | + | 4 | x | x | = | 640 |