4 | ( | ( | 20 | + | a | ) | ( | 500 | − | 20 | a | ) | − | 16000 | ) | = | 3 | ( | ( | 20 | + | a | ) | × | 400 | ) |
方程左边 = | 4 | ( | 20 | + | a | ) | ( | 500 | − | 20 | a | ) | − | 4 | × | 16000 |
= | 4 | ( | 20 | + | a | ) | ( | 500 | − | 20 | a | ) | − | 64000 |
= | 4 | × | 20 | ( | 500 | − | 20 | a | ) | + | 4 | a | ( | 500 | − | 20 | a | ) | − | 64000 |
= | 80 | ( | 500 | − | 20 | a | ) | + | 4 | a | ( | 500 | − | 20 | a | ) | − | 64000 |
= | 80 | × | 500 | − | 80 | × | 20 | a | + | 4 | a | ( | 500 | − | 20 | a | ) | − | 64000 |
= | 40000 | − | 1600 | a | + | 4 | a | ( | 500 | − | 20 | a | ) | − | 64000 |
= | - | 24000 | − | 1600 | a | + | 4 | a | ( | 500 | − | 20 | a | ) |
= | - | 24000 | − | 1600 | a | + | 4 | a | × | 500 | − | 4 | a | × | 20 | a |
= | - | 24000 | − | 1600 | a | + | 2000 | a | − | 80 | a | a |
= | - | 24000 | + | 400 | a | − | 80 | a | a |
- | 24000 | + | 400 | a | − | 80 | a | a | = | 3 | ( | ( | 20 | + | a | ) | × | 400 | ) |
方程右边 = | 3 | ( | 20 | + | a | ) | × | 400 |
= | 1200 | ( | 20 | + | a | ) |
= | 1200 | × | 20 | + | 1200 | a |
= | 24000 | + | 1200 | a |
- | 24000 | + | 400 | a | − | 80 | a | a | = | 24000 | + | 1200 | a |