The set of people who speak English, the set of people who speak English with an Australian accent -
correct answer There exist people who speak English without an Australian accent. However
everyone who speak English with an Australian accent speaks English. Thus we see that the first set is
not a subset of the second, but the second set is a subset of the first.
The set of fruits , the set of citrus fruits - correct answer There exist fruits that are not citrus fruits;
however, every citrus fruits is a fruit. Thus we see that the first set is not a subset of the second, but the
second set is the subset of the first.
The set of student studying discrete mathematics, the set of students studying data structures. - correct
answer There exist student who are studying discrete mathematics and not studying data structures,
and there exist students who are studying data structures and not studying discrete mathematics. Thus
we see that neither set is a subset of the other.
P(x): x^3 > 1 - correct answer For any integer x, x^3>1 if and only if x>1. Thus we see that the truth set
of P(x) is Z^+, the set of positive integers.
Q(x) : x^2 = 2 - correct answer There does not exist any integer x such that x^2 = 2 we seet that the
turth set of Q(x) is Ø the empty set.
R(x) : x< x^2 - correct answer For any integer x, x<x^2 if and only if
x^2 > x
x^2-x > 0
x(x - 1) > 0