(N – 1) - 1 D/ (N + 1)
167. Đơn giản tổng:
A (1
2
1 1).1! (2
2
2 1).2! (3
2
3 1).3! .... (n
2
n 1).n!
a/(n 1)! 1
b/ (n + 2)! – 1c/ (n – 1)!(n – 1) - 1 d/ (n + 1)!(n + 1) - 11
1
1
1
A (1
2
1 1).1! (2
2
2 1).2! (3
2
3 1).3! .... (n
2
n 1).n!
a/(n 1)! 1
b/ (n + 2)! – 1c/ (n – 1)!(n – 1) - 1 d/ (n + 1)!(n + 1) - 11
1
1
1