| 90 | × | 90 | x | x | + | 600 | × | 600 | ( | 120 | × | 120 | − | 240 | x | + | x | x | ) | = | 1 |
| 方程左边 = | 8100 | x | x | + | 360000 | ( | 120 | × | 120 | − | 240 | x | + | x | x | ) |
| 8100 | x | x | + | 360000 | ( | 120 | × | 120 | − | 240 | x | + | x | x | ) | = | 1 |
| 方程左边 = | 8100 | x | x | + | 360000 | × | 120 | × | 120 | − | 360000 | × | 240 | x | + | 360000 | x | x |
| = | 8100 | x | x | + | 5184000000 | − | 86400000 | x | + | 360000 | x | x |
| 8100 | x | x | + | 5184000000 | − | 86400000 | x | + | 360000 | x | x | = | 1 |