| ( | 2400 | ( | x | + | 1 | ) | ) | ( | x | + | 1 | ) | = | 3456 |
| 方程左边 = | 2400 | ( | x | + | 1 | ) | ( | x | + | 1 | ) |
| = | 2400 | x | ( | x | + | 1 | ) | + | 2400 | × | 1 | ( | x | + | 1 | ) |
| = | 2400 | x | ( | x | + | 1 | ) | + | 2400 | ( | x | + | 1 | ) |
| = | 2400 | x | x | + | 2400 | x | × | 1 | + | 2400 | ( | x | + | 1 | ) |
| = | 2400 | x | x | + | 2400 | x | + | 2400 | ( | x | + | 1 | ) |
| = | 2400 | x | x | + | 2400 | x | + | 2400 | x | + | 2400 | × | 1 |
| = | 2400 | x | x | + | 2400 | x | + | 2400 | x | + | 2400 |
| = | 2400 | x | x | + | 4800 | x | + | 2400 |
| 2400 | x | x | + | 4800 | x | + | 2400 | = | 3456 |
| x1= | - | 11 5 |
| x2= | 1 5 |