| 5 | x | ( | 5 | + | 2 | x | ) | × | 2 | + | ( | 2 | x | × | 5 | ) | × | 2 | = | 40 |
| 方程左边 = | 10 | x | ( | 5 | + | 2 | x | ) | + | ( | 2 | x | × | 5 | ) | × | 2 |
| 10 | x | ( | 5 | + | 2 | x | ) | + | ( | 2 | x | × | 5 | ) | × | 2 | = | 40 |
| 方程左边 = | 10 | x | × | 5 | + | 10 | x | × | 2 | x | + | ( | 2 | x | × | 5 | ) | × | 2 |
| = | 50 | x | + | 20 | x | x | + | ( | 2 | x | × | 5 | ) | × | 2 |
| = | 50 | x | + | 20 | x | x | + | 2 | x | × | 5 | × | 2 |
| = | 50 | x | + | 20 | x | x | + | 20 | x |
| = | 70 | x | + | 20 | x | x |
| 70 | x | + | 20 | x | x | = | 40 |
| x2= | 1 2 |