Question

Let A be the set of all students of a boys school. Show that the relation R
in A given by R = {(a,b) :ais sister of b} is the empty relation and R
′
= {(a,b) : the difference between heights of a and b is less than 3 meters} is the universal relation

Answer 1

@terenzreignz

Answer 2

I don't know what a universal relation is, but the relation R is rather interesting...
of course no two elements of A would be related as sisters, they're BOYS for goodness' sake :D

Answer 3

Thank you Sir