| ( | ( | 250 | − | x | ) | − | ( | 225 2 | − | 25 2 | ) | ) | × | 4800 | = | 660000 |
| 方程左边 = | ( | 250 | − | x | ) | × | 4800 | − | ( | 225 2 | − | 25 2 | ) | × | 4800 |
| = | 250 | × | 4800 | − | x | × | 4800 | − | ( | 225 2 | − | 25 2 | ) | × | 4800 |
| = | 1200000 | − | x | × | 4800 | − | ( | 225 2 | − | 25 2 | ) | × | 4800 |
| = | 1200000 | − | 4800 | x | − | 225 2 | × | 4800 | + | 25 2 | × | 4800 |
| = | 1200000 | − | 4800 | x | − | 540000 | + | 60000 |
| = | 720000 | − | 4800 | x |
| 720000 | − | 4800 | x | = | 660000 |
| - | 4800 | x | = | 660000 | − | 720000 |
| - | 4800 | x | = | - | 60000 |
| 60000 | = | 4800 | x |
| 4800 | x | = | 60000 |
| x | = | 60000 | ÷ | 4800 |
| = | 60000 | × | 1 4800 |
| = | 25 | × | 1 2 |
| x | = | 25 2 |
| x | = | 12.5 |