| 3 | ( | 1 | + | X | ) | ( | 1 | + | X | ) | = | 27 4 |
| 方程左边 = | 3 | × | 1 | ( | 1 | + | X | ) | + | 3 | X | ( | 1 | + | X | ) |
| = | 3 | ( | 1 | + | X | ) | + | 3 | X | ( | 1 | + | X | ) |
| = | 3 | × | 1 | + | 3 | X | + | 3 | X | ( | 1 | + | X | ) |
| = | 3 | + | 3 | X | + | 3 | X | ( | 1 | + | X | ) |
| = | 3 | + | 3 | X | + | 3 | X | × | 1 | + | 3 | X | X |
| = | 3 | + | 3 | X | + | 3 | X | + | 3 | X | X |
| = | 3 | + | 6 | X | + | 3 | X | X |
| 3 | + | 6 | X | + | 3 | X | X | = | 27 4 |
| X1= | - | 5 2 |
| X2= | 1 2 |