49 5 | ÷ | 59290000 | = | ( | 390000 | + | r | ) | ( | 390000 | + | r | ) | ÷ | r | ÷ | r | ÷ | r |
| 方程两边同时乘以: | r |
49 5 | ÷ | 59290000 | × | r | = | ( | 390000 | + | r | ) | ( | 390000 | + | r | ) | ÷ | r | ÷ | r |
49 5 | ÷ | 59290000 | × | r | = | 390000 | ( | 390000 | + | r | ) | ÷ | r | ÷ | r | + | r | ( | 390000 | + | r | ) | ÷ | r | ÷ | r |
1 6050000 | r | = | 390000 | ( | 390000 | + | r | ) | ÷ | r | ÷ | r | + | r | ( | 390000 | + | r | ) | ÷ | r | ÷ | r |
| 方程两边同时乘以: | r |
1 6050000 | r | r | = | 390000 | ( | 390000 | + | r | ) | ÷ | r | + | 1 | ( | 390000 | + | r | ) | ÷ | 1 | ÷ | r | × | r |
1 6050000 | r | r | = | 390000 | × | 390000 | ÷ | r | + | 390000 | r | ÷ | r | + | 1 | ( | 390000 | + | r | ) | ÷ | 1 | ÷ | r | × | r |