| b | ÷ | ( | b | + | 4 | ) | = | ( | b | + | 4 | ) | ÷ | ( | - | b | ) |
| 方程两边同时乘以: | ( | b | + | 4 | ) | , | ( | - | b | ) |
| b | ( | - | b | ) | = | ( | b | + | 4 | ) | ( | b | + | 4 | ) |
| - | b | b | = | ( | b | + | 4 | ) | ( | b | + | 4 | ) |
| - | b | b | = | b | ( | b | + | 4 | ) | + | 4 | ( | b | + | 4 | ) |
| - | b | b | = | b | b | + | b | × | 4 | + | 4 | ( | b | + | 4 | ) |
| - | b | b | = | b | b | + | 4 | b | + | 4 | b | + | 4 | × | 4 |
| - | b | b | = | b | b | + | 4 | b | + | 4 | b | + | 16 |
| - | b | b | = | b | b | + | 8 | b | + | 16 |