( | y | − | 20 | ) | ( | - | 10 | y | + | 530 | ) | = | 2340 |
方程左边 = | y | ( | - | 10 | y | + | 530 | ) | − | 20 | ( | - | 10 | y | + | 530 | ) |
= | - | y | × | 10 | y | + | y | × | 530 | − | 20 | ( | - | 10 | y | + | 530 | ) |
= | - | y | × | 10 | y | + | 530 | y | + | 20 | × | 10 | y | − | 20 | × | 530 |
= | - | y | × | 10 | y | + | 530 | y | + | 200 | y | − | 10600 |
= | - | y | × | 10 | y | + | 730 | y | − | 10600 |
- | y | × | 10 | y | + | 730 | y | − | 10600 | = | 2340 |