19 20 | n | ( | n | − | 1 | ) | ( | n | − | 2 | ) | ( | n | − | 3 | ) | ( | n | − | 4 | ) | = | ( | n | − | 5 | ) | ( | n | − | 6 | ) | ( | n | − | 7 | ) | ( | n | − | 8 | ) | ( | n | − | 9 | ) |
方程左边 = | 19 20 | n | n | ( | n | − | 2 | ) | ( | n | − | 3 | ) | ( | n | − | 4 | ) | − | 19 20 | n | × | 1 | ( | n | − | 2 | ) | ( | n | − | 3 | ) | ( | n | − | 4 | ) |
= | 19 20 | n | n | ( | n | − | 2 | ) | ( | n | − | 3 | ) | ( | n | − | 4 | ) | − | 19 20 | n | ( | n | − | 2 | ) | ( | n | − | 3 | ) | ( | n | − | 4 | ) |
= | 19 20 | n | n | n | ( | n | − | 3 | ) | ( | n | − | 4 | ) | − | 19 20 | n | n | × | 2 | ( | n | − | 3 | ) | ( | n | − | 4 | ) |
= | 19 20 | n | n | n | ( | n | − | 3 | ) | ( | n | − | 4 | ) | − | 19 10 | n | n | ( | n | − | 3 | ) | ( | n | − | 4 | ) | − | 19 20 |
= | 19 20 | n | n | n | n | ( | n | − | 4 | ) | − | 19 20 | n | n | n | × | 3 | ( | n | − | 4 | ) |
= | 19 20 | n | n | n | n | ( | n | − | 4 | ) | − | 57 20 | n | n | n | ( | n | − | 4 | ) | − | 19 10 |
= | 19 20 | n | n | n | n | n | − | 19 20 | n | n | n | n | × | 4 |
= | 19 20 | n | n | n | n | n | − | 19 5 | n | n | n | n | − | 57 20 |
= | 19 20 | n | n | n | n | n | − | 19 5 | n | n | n | n | − | 57 20 |
= | 19 20 | n | n | n | n | n | − | 19 5 | n | n | n | n | − | 57 20 |
= | 19 20 | n | n | n | n | n | − | 19 5 | n | n | n | n | − | 57 20 |
= | 19 20 | n | n | n | n | n | − | 19 5 | n | n | n | n | − | 57 20 |
= | 19 20 | n | n | n | n | n | − | 19 5 | n | n | n | n | − | 57 20 |
= | 19 20 | n | n | n | n | n | − | 19 5 | n | n | n | n | − | 57 20 |
= | 19 20 | n | n | n | n | n | − | 19 5 | n | n | n | n | − | 57 20 |
= | 19 20 | n | n | n | n | n | − | 19 5 | n | n | n | n | − | 57 20 |
= | 19 20 | n | n | n | n | n | − | 19 5 | n | n | n | n | − | 57 20 |
= | 19 20 | n | n | n | n | n | − | 19 5 | n | n | n | n | − | 57 20 |
= | 19 20 | n | n | n | n | n | − | 19 5 | n | n | n | n | − | 57 20 |
= | 19 20 | n | n | n | n | n | − | 19 5 | n | n | n | n | − | 57 20 |
= | 19 20 | n | n | n | n | n | − | 19 5 | n | n | n | n | − | 57 20 |
= | 19 20 | n | n | n | n | n | − | 19 5 | n | n | n | n | − | 57 20 |
= | 19 20 | n | n | n | n | n | − | 19 5 | n | n | n | n | − | 57 20 |
= | 19 20 | n | n | n | n | n | − | 19 5 | n | n | n | n | − | 57 20 |
= | 19 20 | n | n | n | n | n | − | 19 5 | n | n | n | n | − | 57 20 |