| ( | 40 | − | 25 | − | a | ) | ( | 400 | ( | 1 | + | 1 4 | ) | × | 5 | a | ) | = | 4250 |
| 方程左边 = | 40 | ( | 400 | ( | 1 | + | 1 4 | ) | × | 5 | a | ) | − | 25 | ( | 400 | ( | 1 | + | 1 4 | ) | × | 5 | a | ) | − | a | ( | 400 | ( | 1 | + | 1 4 | ) | × | 5 | a | ) |
| = | 40 | × | 400 | ( | 1 | + | 1 4 | ) | × | 5 | a | − | 25 | ( | 400 | ( | 1 | + | 1 4 | ) | × | 5 | a | ) | − | a | ( | 400 | ( | 1 | + | 1 4 | ) | × | 5 | a | ) |
| = | 80000 | ( | 1 | + | 1 4 | ) | a | − | 25 | ( | 400 | ( | 1 | + | 1 4 | ) | × | 5 | a | ) | − | a | ( | 400 | ( | 1 | + | 1 4 | ) | × | 5 | a | ) |
| = | 80000 | × | 1 | a | + | 80000 | × | 1 4 | a | − | 25 | ( | 400 | ( | 1 | + | 1 4 | ) | × | 5 | a | ) | − | a | ( | 400 | ( | 1 | + | 1 4 | ) | × | 5 | a | ) |
| = | 80000 | a | + | 20000 | a | − | 25 | ( | 400 | ( | 1 | + | 1 4 | ) | × | 5 | a | ) | − | a | ( | 400 | ( | 1 | + | 1 4 | ) | × | 5 | a | ) |
| = | 100000 | a | − | 25 | ( | 400 | ( | 1 | + | 1 4 | ) | × | 5 | a | ) | − | a | ( | 400 | ( | 1 | + | 1 4 | ) | × | 5 | a | ) |
| = | 100000 | a | − | 25 | × | 400 | ( | 1 | + | 1 4 | ) | × | 5 | a | − | a | ( | 400 | ( | 1 | + | 1 4 | ) | × | 5 | a | ) |
| = | 100000 | a | − | 50000 | ( | 1 | + | 1 4 | ) | a | − | a | ( | 400 | ( | 1 | + | 1 4 | ) | × | 5 | a | ) |
| = | 100000 | a | − | 50000 | × | 1 | a | − | 50000 | × | 1 4 | a | − | a | ( | 400 | ( | 1 | + | 1 4 | ) | × | 5 | a | ) |
| = | 100000 | a | − | 50000 | a | − | 12500 | a | − | a | ( | 400 | ( | 1 | + | 1 4 | ) | × | 5 | a | ) |
| = | 37500 | a | − | a | ( | 400 | ( | 1 | + | 1 4 | ) | × | 5 | a | ) |
| = | 37500 | a | − | a | × | 400 | ( | 1 | + | 1 4 | ) | × | 5 | a |
| = | 37500 | a | − | a | × | 2000 | ( | 1 | + | 1 4 | ) | a |
| = | 37500 | a | − | a | × | 2000 | × | 1 | a | − | a | × | 2000 | × | 1 4 | a |
| = | 37500 | a | − | a | × | 2000 | a | − | a | × | 500 | a |
| 37500 | a | − | a | × | 2000 | a | − | a | × | 500 | a | = | 4250 |