| 120000 | ( | 1 | + | 4 | t | ) | ( | 1 | + | t | ) | = | 120000 | + | 840000 | t |
| 方程左边 = | 120000 | × | 1 | ( | 1 | + | t | ) | + | 120000 | × | 4 | t | ( | 1 | + | t | ) |
| = | 120000 | ( | 1 | + | t | ) | + | 480000 | t | ( | 1 | + | t | ) |
| = | 120000 | × | 1 | + | 120000 | t | + | 480000 | t | ( | 1 | + | t | ) |
| = | 120000 | + | 120000 | t | + | 480000 | t | ( | 1 | + | t | ) |
| = | 120000 | + | 120000 | t | + | 480000 | t | × | 1 | + | 480000 | t | t |
| = | 120000 | + | 120000 | t | + | 480000 | t | + | 480000 | t | t |
| = | 120000 | + | 600000 | t | + | 480000 | t | t |
| 120000 | + | 600000 | t | + | 480000 | t | t | = | 120000 | + | 840000 | t |
| t2= | 1 2 |