( | 9 | + | x | ) | ( | 9 | − | x | ) | × | 1 2 | = | 36 |
方程左边 = | 9 | ( | 9 | − | x | ) | × | 1 2 | + | x | ( | 9 | − | x | ) | × | 1 2 |
= | 9 2 | ( | 9 | − | x | ) | + | x | ( | 9 | − | x | ) | × | 1 2 |
= | 9 2 | × | 9 | − | 9 2 | x | + | x | ( | 9 | − | x | ) | × | 1 2 |
= | 81 2 | − | 9 2 | x | + | x | ( | 9 | − | x | ) | × | 1 2 |
= | 81 2 | − | 9 2 | x | + | x | × | 9 | × | 1 2 | − | x | x | × | 1 2 |
= | 81 2 | − | 9 2 | x | + | x | × | 9 2 | − | x | x | × | 1 2 |
= | 81 2 | − | 0 | x | − | x | x | × | 1 2 |
81 2 | − | x | x | × | 1 2 | = | 36 |