20 | x | = | x | ( | 10 | + | 10 | + | ( | x | − | 1 | ) | × | 2 | ) | × | 1 2 |
方程右边 = | x | × | 10 | × | 1 2 | + | x | × | 10 | × | 1 2 | + | x | ( | x | − | 1 | ) | × | 2 | × | 1 2 |
= | x | × | 5 | + | x | × | 5 | + | x | ( | x | − | 1 | ) | × | 1 |
= | 10 | x | + | x | ( | x | − | 1 | ) | × | 1 |
= | 10 | x | + | x | x | × | 1 | − | x | × | 1 | × | 1 |
= | 10 | x | + | x | x | × | 1 | − | x | × | 1 |
= | 9 | x | + | x | x | × | 1 |
20 | x | = | 9 | x | + | x | x | × | 1 |