69 10 | x | − | 390 | = | ( | 6 | x | − | 600 | ) | x | ( | 1 | + | 20 100 | ) |
| 方程右边 = | 6 | x | x | ( | 1 | + | 20 100 | ) | − | 600 | x | ( | 1 | + | 20 100 | ) |
| = | 6 | x | x | × | 1 | + | 6 | x | x | × | 20 100 | − | 600 | x | ( | 1 | + | 20 100 | ) |
| = | 6 | x | x | + | 6 5 | x | x | − | 600 | x | ( | 1 | + | 20 100 | ) |
| = | 6 | x | x | + | 6 5 | x | x | − | 600 | x | × | 1 | − | 600 | x | × | 20 100 |
| = | 6 | x | x | + | 6 5 | x | x | − | 600 | x | − | 120 | x |
| = | 6 | x | x | + | 6 5 | x | x | − | 720 | x |
69 10 | x | − | 390 | = | 6 | x | x | + | 6 5 | x | x | − | 720 | x |