| ( | 1 | ÷ | a | − | 4 | ) | + | ( | 2 | ÷ | 1 | − | 2 | a | ) | = | ( | 1 | ÷ | a | − | 2 | ) | + | ( | 4 | ÷ | 1 | − | 4 | a | ) |
| 1 | ÷ | a | − | 4 | + | ( | 2 | ÷ | 1 | − | 2 | a | ) | = | ( | 1 | ÷ | a | − | 2 | ) | + | ( | 4 | ÷ | 1 | − | 4 | a | ) |
| 1 | ÷ | a | − | 4 | + | ( | 2 | ÷ | 1 | − | 2 | a | ) | = | 1 | ÷ | a | − | 2 | + | ( | 4 | ÷ | 1 | − | 4 | a | ) |
| 方程两边同时乘以: | a |
| 1 | − | 4 | a | + | ( | 2 | ÷ | 1 | − | 2 | a | ) | a | = | 1 | ÷ | 1 | × | 1 | − | 2 | a | + | ( | 4 | ÷ | 1 | − | 4 | a | ) | a |
| 1 | − | 4 | a | + | 2 | ÷ | 1 | × | a | − | 2 | a | a | = | 1 | ÷ | 1 | × | 1 | − | 2 | a | + | ( | 4 | ÷ | 1 | − | 4 | a | ) | a |
| 1 | − | 4 | a | + | 2 | ÷ | 1 | × | a | − | 2 | a | a | = | 1 | ÷ | 1 | × | 1 | − | 2 | a | + | 4 | ÷ | 1 | × | a | − | 4 | a | a |
| 1 | − | 4 | a | + | 2 | a | − | 2 | a | a | = | 1 | − | 2 | a | + | 4 | a | − | 4 | a | a |
| 1 | − | 2 | a | − | 2 | a | a | = | 1 | + | 2 | a | − | 4 | a | a |