| ( | 3 | − | 5 | a | ) | ( | 1620 | + | 810 | a | ) | = | 3564 |
| 方程左边 = | 3 | ( | 1620 | + | 810 | a | ) | − | 5 | a | ( | 1620 | + | 810 | a | ) |
| = | 3 | × | 1620 | + | 3 | × | 810 | a | − | 5 | a | ( | 1620 | + | 810 | a | ) |
| = | 4860 | + | 2430 | a | − | 5 | a | ( | 1620 | + | 810 | a | ) |
| = | 4860 | + | 2430 | a | − | 5 | a | × | 1620 | − | 5 | a | × | 810 | a |
| = | 4860 | + | 2430 | a | − | 8100 | a | − | 4050 | a | a |
| = | 4860 | − | 5670 | a | − | 4050 | a | a |
| 4860 | − | 5670 | a | − | 4050 | a | a | = | 3564 |
| a1= | - | 8 5 |
| a2= | 1 5 |