:
N ,
Z ,
Z0 ,
Q ,
I ,
R .
9 . , , , .
, , , (R). R , , (). 3 :
I.
1. a + b = b + a
2. a + (b + c)= (a + b) + c
3. a ∙ b = b ∙ a
4. a ∙ (b ∙ c)= (a ∙ b) ∙ c
5. (a + b) ∙ c= a ∙ c + b ∙ c
6. 0 , + 0 =
7. , + ( ) = 0
8. 1≠0 , ∙ 1 =
9. ≠0 1 , ∙ 1 = 1
II.
1. , .
2. , x=y.
3. , .
4. ≤ , z + z ≤ + z
5. ≤ , z > 0 ∙ z ≤ ∙ z,
z < 0 ∙ z ≥ ∙ z.
III. . X Y . , , , .
.
, , IIII.
.
0 . 0 . , . 0 ( ). , , 0, , .
. :
1) x >0. 0 x. x .
2) x <0. 0 ( x). x .
|
|
3) x =0, 0.
. :
1) x . x >0, 0 x.
2) x . x <0, 0 x,
3) x . x =0.
, . R ( ) , , .. , . , . .