n n + 1 -1 n +1 1 1 1
--------- = --------------- = ----------- - -------- = ----- - ------
( n+1 )! (n+1 ) ! ( n+1)! ( n +1 )! n! ( n+1)!
daca n=1 1/2! = 1/1! - 1/2!
n=2 2/3!= 1/2! - 1/3!
n=3 3/4!= 1/3! - 1/4!
.....................................................
n/(n+1)! = 1/n! - 1/(n+1)!
adunarea = 1 - 1/(n+1)!