( | - | 4 | + | 2 5 | x | ) | ( | - | 4 | + | 2 5 | x | ) | = | 0 |
方程左边 = | - | 4 | ( | - | 4 | + | 2 5 | x | ) | + | 2 5 | x | ( | - | 4 | + | 2 5 | x | ) |
= | 4 | × | 4 | − | 4 | × | 2 5 | x | + | 2 5 | x | ( | - | 4 | + | 2 5 | x | ) |
= | 16 | − | 8 5 | x | + | 2 5 | x | ( | - | 4 | + | 2 5 | x | ) |
= | 16 | − | 8 5 | x | − | 2 5 | x | × | 4 | + | 2 5 | x | × | 2 5 | x |
= | 16 | − | 8 5 | x | − | 8 5 | x | + | 4 25 | x | x |
= | 16 | − | 16 5 | x | + | 4 25 | x | x |
16 | − | 16 5 | x | + | 4 25 | x | x | = | 0 |