| 160 | ( | 1 | + | a% | ) | × | 100 | ( | 1 | − | 4 5 | a | ) | = | 16000 |
| 方程左边 = | 16000 | ( | 1 | + | a% | ) | ( | 1 | − | 4 5 | a | ) |
| 16000 | ( | 1 | + | a% | ) | ( | 1 | − | 4 5 | a | ) | = | 16000 |
| 方程左边 = | 16000 | × | 1 | ( | 1 | − | 4 5 | a | ) | + | 16000 | × | a% | ( | 1 | − | 4 5 | a | ) |
| = | 16000 | ( | 1 | − | 4 5 | a | ) | + | 160 | a | ( | 1 | − | 4 5 | a | ) |
| = | 16000 | × | 1 | − | 16000 | × | 4 5 | a | + | 160 | a | ( | 1 | − | 4 5 | a | ) |
| = | 16000 | − | 12800 | a | + | 160 | a | ( | 1 | − | 4 5 | a | ) |
| = | 16000 | − | 12800 | a | + | 160 | a | × | 1 | − | 160 | a | × | 4 5 | a |
| = | 16000 | − | 12800 | a | + | 160 | a | − | 128 | a | a |
| = | 16000 | − | 12640 | a | − | 128 | a | a |
| 16000 | − | 12640 | a | − | 128 | a | a | = | 16000 |
| a1=0 |