, n k , , n-k . n(k). , 5 (3) , 3 , , 2 .
:
n(k) = 
pk qn-k
n(k) = 
pk qn-k (1)
, . (1) :
(p+q)n = 
pn + 
pn-1q ++ 
pkqn-k ++ 
n
. , , 0,75.
, 6 4 .
. q=1-p=1-0,75= 0,25.
6 (4) = 
p4 q2 = 
(0,75)4 ∙(0,25)2 = 0,30.
n , . :
n(k) ≈ 
∙ φ (x),
= (k - np)/ 
.
, , .
. .
, , , .. . ( )
.
() = 11+ 22+.+ npn
,
() = 
xi pi
.
1) :
() =
2) :
() = ѷ()
3) :
(1 + 2 + + n) = (1) + (2) +... + (n)
4) :
(1 2 ... n) = (1) (2) ... (n)
