Let {Kn : n ∈ N} be a collection of nonempty compact subsets of
R N...
Let {Kn : n ∈ N} be a collection of nonempty compact subsets of
R N such that for all n, Kn+1 ⊂ Kn. Show that K = T∞ n=1 Kn is
compact. Can K ever be the empty set?
Let S ⊆ R be a nonempty compact set and p ∈ R. Prove that there
exists a point x_0 ∈ S which is “closest” to p. That is, prove that
there exists x0 ∈ S such that |x_0 − p| is minimal.
Let A ⊂ R be a nonempty discrete set
a. Show that A is at most countable
b. Let f: A →R be any function, and let p ∈ A be any point. Show
that f is continuous at p
Let Ω be any set and let F be the collection of all subsets of Ω
that are either countable or have a countable complement. (Recall
that a set is countable if it is either finite or can be placed in
one-to-one correspondence with the natural numbers N = {1, 2, . .
.}.)
(a) Show that F is a σ-algebra.
(b) Show that the set function given by
μ(E)= 0 if E is countable ;
μ(E) = ∞ otherwise...
Suppose we have a collection of n different subsets of the set {
1, 2, ..., n } and they are in some arbitrary order, that is, we
have subsets S1, S2, ..., Sn, but how many and which elements are
in each of these subsets is entirely arbitrary. Suppose also that
we have another subset S' of { 1, 2, ..., n }.
(a) Express a brute-force algorithm that determines whether S'
equal to one of the subsets in...
Let S be a set of n numbers. Let X be
the set of all subsets of S of size k, and let
Y be the set of all ordered k-tuples
(s1, s2, ,
sk)
such that
s1 < s2
< < sk.
That is,
X
=
{{s1, s2, ,
sk} | si S and all si's
are distinct}, and
Y
=
{(s1, s2, ,
sk) | si S and s1 <
s2 < < sk}.
(a) Define a one-to-one correspondence
f : X → Y.
Explain...
Let (E,d) be a metric space and K, K' disjoint compact subsets
of E. Prove the existence of disjoint open sets U and U' containing
K and K' respectively.
Let S(n) be the number of subsets of {1,2,...,n} having the
following property: there are no three elements in the subset that
are consecutive integers. Find a recurrence for S(n) and explain in
words why S(n) satisfies this recurrence
Let A and B be two non empty bounded subsets of R:
1) Let A +B = { x+y/ x ∈ A and y ∈ B} show that sup(A+B)= sup A
+ sup B
2) For c ≥ 0, let cA= { cx /x ∈ A} show that sup cA = c sup
A
hint:( show c supA is a U.B for cA and show if l < csupA then
l is not U.B)
Definition 1 (Topological space). Let X be a set. A collection O
of subsets of X is called a topology on the set X if the following
properties are satisfied:
(1) emptyset ∈ O and X ∈ O.
(2) For all A,B ∈ O, we have A∩B ∈ O (stability under
intersection).
(3) For all index sets I, and for all collections {Ui}i∈I of
elements of O (i.e., Ui ∈ O for all i ∈ I), we have U i∈I...