- , .
. , , ..
- , , . .
, , , , , , .
? . . , , , .
.., .
, .
= n (), .
: 0 = n (Ø).
. , .
4. N0
. :
= n (), = n (). , , .. = .
a , .
= ~ , n () = , n () =
n () = , n () = , ( < ), ( > ).
< ~ , , ≠ , ≠ Ø
∆ ∆ ∆ ∆ ∆
1
, 2 =2, 2 < 3,3 < 4 .. : , , ..
|
|
, 20, .. .
.
< , = n (), = n () ~ , 1 .
.. 1 , = 1 n() = n (1 ) n() = n (1) + n ( ) (*)
... ~ n ( ) = n ().
n ( ) = . * = +
.. , < , = + , .
, , + =
3 < 7, .. 4, 3 + 4 = 7.
. :
7 + 1 = 8, 7 < 8 5 + 1 = 6, 5 < 6
.
< . :
≤ , < . , < N N. .
, N N.
< N N N ≠ N
3 < 7, . {1, 2, 3} {1, 2, 3, 4, 5, 6, 7}
, .
: , , , .