Which of the following relations define functions? SELECT ALL
THAT APPLY
A. Let R1 be the relation on ℝ × ℝ,
R1 = {(x, y) | x ∈ ℝ and x = y3}, where
ℝ denotes the set of real numbers.
B. Consider the set S = {1, 2, 3, 4} and let R be the relation
on S × S, R = {(2,1), (1,2), (3,2), (2,3), (4,3), (3,4)}.
C. Consider the sets S1 = {1, 2, 3} and
S2 = {1, 2, 3, 4} and let R be the relation on
S1 × S2, R = {(1,1), (2,2), (3,3),
(3,4)}.
D. Consider the set S = {5, 6, 7, 8} and let R be the relation
on S × S, R = {(5,8), (6,7), (7,6), (8,5)}.