| ( | 1 4 | − | x | ) | ( | 3 20 | − | x | ) | ÷ | ( | 1 20 | + | x | ) | = | 9 20 |
| 方程两边同时乘以: | ( | 1 20 | + | x | ) |
| ( | 1 4 | − | x | ) | ( | 3 20 | − | x | ) | = | 9 20 | ( | 1 20 | + | x | ) |
1 4 | ( | 3 20 | − | x | ) | − | x | ( | 3 20 | − | x | ) | = | 9 20 | ( | 1 20 | + | x | ) |
1 4 | ( | 3 20 | − | x | ) | − | x | ( | 3 20 | − | x | ) | = | 9 20 | × | 1 20 | + | 9 20 | x |
1 4 | ( | 3 20 | − | x | ) | − | x | ( | 3 20 | − | x | ) | = | 9 400 | + | 9 20 | x |
1 4 | × | 3 20 | − | 1 4 | x | − | x | ( | 3 20 | − | x | ) | = | 9 400 | + | 9 20 | x |
3 80 | − | 1 4 | x | − | x | ( | 3 20 | − | x | ) | = | 9 400 | + | 9 20 | x |
3 80 | − | 1 4 | x | − | x | × | 3 20 | + | x | x | = | 9 400 | + | 9 20 | x |
3 80 | − | 2 5 | x | + | x | x | = | 9 400 | + | 9 20 | x |