39. f A B , (a, b) f (a, c) f b = c.
A
B A B
, .
40. f A B A B, Dom f = A,
f: A B A B.
A f
B
. f: A B , a A b B f (a)= b (a, b) f a f b.
41. f: A B , a A, b B. f (a)= b, b a f; a b f.
A
f
B
42. f: A B, A 0 A. f (A 0)={ f (a)| a A 0} A 0 f.
A B
f
f (A 0)
43. f: A B , b B.
f -1(b)={ a A | f (a)= b } b f.
A
B
a1, a2 b.
{ a 1, a 2} f.
44. f: A B , B 0 B.
f -1(B 0)= B 0 f.
, f -1(B)= A, f (A) B.
45. f: X Y ( - X Y), x 1, x 2 X x 1 x 2 f (x 1) f (x 2).
. .
46. f: X Y , x 1, x 2 X f(x 1)= f (x 2) x 1= x 2. ,
47. f: X Y ( X Y), Im f Y (Im f = Y), . .
y Y x X . f (x) = y.
48. f: X Y (- X Y), f .
, , .
A f B
f B
A ,
A B
f
,