| ( | 2 | d | + | 4 | ) | ÷ | ( | d | d | + | 4 | d | + | 20 | ) | = | 1 | ÷ | ( | d | + | 4 | ) |
| 方程两边同时乘以: | ( | d | d | + | 4 | d | + | 20 | ) | , | ( | d | + | 4 | ) |
| ( | 2 | d | + | 4 | ) | ( | d | + | 4 | ) | = | 1 | ( | d | d | + | 4 | d | + | 20 | ) |
| 2 | d | ( | d | + | 4 | ) | + | 4 | ( | d | + | 4 | ) | = | 1 | ( | d | d | + | 4 | d | + | 20 | ) |
| 2 | d | ( | d | + | 4 | ) | + | 4 | ( | d | + | 4 | ) | = | 1 | d | d | + | 1 | × | 4 | d | + | 1 | × | 20 |
| 2 | d | ( | d | + | 4 | ) | + | 4 | ( | d | + | 4 | ) | = | 1 | d | d | + | 4 | d | + | 20 |
| 2 | d | d | + | 2 | d | × | 4 | + | 4 | ( | d | + | 4 | ) | = | 1 | d | d | + | 4 | d | + | 20 |
| 2 | d | d | + | 8 | d | + | 4 | ( | d | + | 4 | ) | = | 1 | d | d | + | 4 | d | + | 20 |
| 2 | d | d | + | 8 | d | + | 4 | d | + | 4 | × | 4 | = | 1 | d | d | + | 4 | d | + | 20 |
| 2 | d | d | + | 8 | d | + | 4 | d | + | 16 | = | 1 | d | d | + | 4 | d | + | 20 |
| 2 | d | d | + | 12 | d | + | 16 | = | 1 | d | d | + | 4 | d | + | 20 |