| ( | a | − | 480 | ) | ÷ | 480 | = | ( | 2 | a | − | 240 | ) | ÷ | ( | a | + | 240 | ) |
| 方程两边同时乘以: | ( | a | + | 240 | ) |
| ( | a | − | 480 | ) | ÷ | 480 | × | ( | a | + | 240 | ) | = | ( | 2 | a | − | 240 | ) |
| a | ÷ | 480 | × | ( | a | + | 240 | ) | − | 480 | ÷ | 480 | × | ( | a | + | 240 | ) | = | ( | 2 | a | − | 240 | ) |
| a | ÷ | 480 | × | ( | a | + | 240 | ) | − | 480 | ÷ | 480 | × | ( | a | + | 240 | ) | = | 2 | a | − | 240 |
| a | × | 1 480 | ( | a | + | 240 | ) | − | 1 | ( | a | + | 240 | ) | = | 2 | a | − | 240 |
| a | × | 1 480 | a | + | a | × | 1 480 | × | 240 | − | 1 | ( | a | + | 240 | ) | = | 2 | a | − | 240 |
| a | × | 1 480 | a | + | a | × | 1 2 | − | 1 | ( | a | + | 240 | ) | = | 2 | a | − | 240 |
| a | × | 1 480 | a | + | 1 2 | a | − | 1 | a | − | 1 | × | 240 | = | 2 | a | − | 240 |
| a | × | 1 480 | a | + | 1 2 | a | − | 1 | a | − | 240 | = | 2 | a | − | 240 |
| a | × | 1 480 | a | − | 1 2 | a | − | 240 | = | 2 | a | − | 240 |