S = ( )N NNC1 − 2 2 + 3 3 − 4 4 + + − 1 −1 (N ∈ Z, N ≥ N

2) - DE THI MON TOAN THAM KHAO
DE THI MON TOAN THAM KHAO

2) Tính tổng: S = ( )

n nn

C

1

− 2

2

+ 3

3

− 4

4

+ + − 1

−1

(n ∈ Z, n ≥ 2)

n

. C . C . C ... . n . C

n