, , . , . . , () ( , ).
19 . . . . , , , N ( ), :
1) N 1, ;
2) n n, n;
: , n, n.
3) 1 () , n, n = 1;
4) n n, m, n m ;
5) - 1 (). , , n, , n , , .
.
+, :
6) n + 1 = n;
7) n + m = (n + m);
∙, :
8) n ∙ 1 = n;
9) n ∙ m = n ∙ m + n.
:
1) (n + m) + k = n + (m + k) n, m, k ( );
2) n + m = m + n n, m ( ).
:
1) (n ∙ m) ∙ k = n ∙ (m ∙ k) n, m, k ();
2) n ∙ m = m ∙ n n, m ();
, , , :
n ∙ (m + k) = n ∙ m + n ∙ k n, m, k ( ).
, , , . , , , : 2 ∙ 2 = 4?
. , 2 + 2 = 4.
.
:
2 + 2 = 2 + 1 = [ 7] (2 + 1) = [ 6] (2) = 3 = 4.
., 2 ∙ 2 = 4.
. :
2 ∙ 2 = 2 ∙ 1 = [ 9] 2 ∙ 1 + 2 = [ 8] 2 + 2.
, 2 + 2 = 4. , , 2 ∙ 2 4!
, , 2, 3 , . , . , , . , , .