Let R be reflexive and transitive relation on a set S. Then R intersect R inverse is a
a)reflexive but not transitive relation.
b)transitive but not reflexive relation.
c)symmetric but not reflexive and transitive relation.
d)equivalence relation.
Let (M,d(x,y)) be a metric space and suppose that E, K are nonempty subsets of M with E closed, K compact, and E, K disjoint. Please show that there is a postive real number mu such that d(x,y) >= mu for every x contained in E and y contained in K, using either the definition of compactness in terms of open coverings or the limit point property.
Give an example of function that is differentiable, its derivative is positive at some point P but there is no neighboorhood of P such that function is monotone there.
Prove that if x is a rational number and y is an irrational number, then x + y is an irrational
number. If, in addition, x is not equal to 1, then show that xy is an irrational number.