Exercises B.3-4

Solution Wanted!

Exercises B.3-3

Let L: X → Y be a binary relation, then
: Y → X is defined by ⇔.

Exercises B.3-2

f is not bijective for N to N, because 1 is not in range.

f is bijective for Z to Z.

Exercises B.3-1

a. If x is in A, then there is one distinct element y in B sucht that f(x) = y. Hence |A| ≤ |B|.

b. If y is in B, then there are at least one distinct elements x in A, such that f(x) = y. hence |A| ≥ |B|.