Page 13 - Discrete Structure II

4. {(c, a), (c, b), (c, c)}
(a, b) and (b, a) are not necessary the same

but {a, b} and {b, a} are the same

Exercise
Consider the following set

A = {1, 2, 3, 4}
A x A = {(1, 1), (1, 2), (1, 3), (1, 4), (2, 1), (2, 2), (2, 3), (2, 4), (3, 1), (3, 2), (3, 3), (3, 4), (4, 1), (4, 2),
(4, 3), (4, 4)}
R = {(a, b) such that a divides b}

Answer:

R = {(1, 1), (2, 2), (3, 3), (4, 4),(1, 2) (1, 3), (1, 4) , (2, 4)}

Answer:

(1, 1) ∈ R 1, R 3, R 4, R 6

(1, 2) ∈ R 1, R 6

(2, 1) ∈ R2, R5, R6

(2, 2) ∈ R1, R3, R4,