| 300 | ( | 1 | − | X | ) | − | 300 | ( | 1 | − | X | ) | ( | 1 | − | 2 | X | ) | = | 144 |
| 方程左边 = | 300 | × | 1 | − | 300 | X | − | 300 | ( | 1 | − | X | ) | ( | 1 | − | 2 | X | ) |
| = | 300 | − | 300 | X | − | 300 | ( | 1 | − | X | ) | ( | 1 | − | 2 | X | ) |
| = | 300 | − | 300 | X | − | 300 | × | 1 | ( | 1 | − | 2 | X | ) | + | 300 | X | ( | 1 | − | 2 | X | ) |
| = | 300 | − | 300 | X | − | 300 | ( | 1 | − | 2 | X | ) | + | 300 | X | ( | 1 | − | 2 | X | ) |
| = | 300 | − | 300 | X | − | 300 | × | 1 | + | 300 | × | 2 | X | + | 300 | X | ( | 1 | − | 2 | X | ) |
| = | 300 | − | 300 | X | − | 300 | + | 600 | X | + | 300 | X | ( | 1 | − | 2 | X | ) |
| = | 0 | + | 300 | X | + | 300 | X | ( | 1 | − | 2 | X | ) |
| = | 300 | X | + | 300 | X | × | 1 | − | 300 | X | × | 2 | X |
| = | 300 | X | + | 300 | X | − | 600 | X | X |
| = | 600 | X | − | 600 | X | X |
| 600 | X | − | 600 | X | X | = | 144 |
| X1= | 2 5 |
| X2= | 3 5 |