( | x | + | 40 | ) | ( | x | − | 72 | ) | = | x | ( | x | − | 40 | ) |
方程左边 = | x | ( | x | − | 72 | ) | + | 40 | ( | x | − | 72 | ) |
= | x | x | − | x | × | 72 | + | 40 | ( | x | − | 72 | ) |
= | x | x | − | 72 | x | + | 40 | x | − | 40 | × | 72 |
= | x | x | − | 72 | x | + | 40 | x | − | 2880 |
= | x | x | − | 32 | x | − | 2880 |
x | x | − | 32 | x | − | 2880 | = | x | ( | x | − | 40 | ) |
方程右边 = | x | x | − | x | × | 40 |
x | x | − | 32 | x | − | 2880 | = | x | x | − | 40 | x |