8. [10 pts] (Carothers 7.46.) If A is a dense subset of a metric space (M, d), show that (A, d) a...
A subset D of a metric space (X, d) is dense if every member of
X is a limit of a sequence of elements from D.
Suppose (X,d) and (Y,ρ) are metric spaces and D is a dense
subset of X.
1. Prove that if f : D -» Y is uniformly continuous then there exists an extension15 of f to a if dn (E D) e X define 7(x) lim f(d,) uniformly continuous function f:X * Y. Hint: 2....
Let X be a non-empty set. Show that the only dense subset of X with respect to the discrete metric ddise is X. The whole set of any metric spaces is always dense, so this question is really asking you to exclude all other possibilities. Show that if (X, d) is a metric space and has dense subset A + X, then (X, d) is not topologically equivalent to (X, ddisc). (Note that this is another way of showing that...
Let (X, d) be a metric space, and let ACX be a subset (a) (3 pts) Let x E X. Write the definition of d(x, A) (b) (7 pts) Assume A is closed. Prove that d(x,A-0 if and only if x E A.
Let (X, d) be a metric space, and let ACX be a subset (a) (3 pts) Let x E X. Write the definition of d(x, A) (b) (7 pts) Assume A is closed. Prove that d(x,A-0 if...
7. Recall the space m of bounded sequences of real numbers together with the metric d(х, у) — suр |2; — Ук). k 1,2. (a) Give a simple proof to show that m is complete by showing that m = suitable space X. (Recall that C(X) denotes the space of continuous bounded real- valued functions on X together with the supremum norm.) C(X) for some (b) Let A denote the unit ball in m given by А 3 (x€ т:...
(a) Suppose K is a compact subset of a metric space (X, d) and x є X but x K Show that there exist disjoint, open subsets of Gi and G2 of (X, d) such that r E Gi and KG2. (Hint: Use the version of compactness we called "having a compact topology." You will also need the Hausdorff property.) b) Now suppose that Ki and K2 are two compact, disjoint subsets of a metric space (X, d). Use (a)...
please explain the steps you take
2. Let M be the set of all measurable sets in R, and let d be our semi-metric, show that (M, d) is complete: If (An)1 is a Cauchy sequence (with our semi- metric d) then there is a measurable set A EM such that lim, too d(An, A) 0.
2. Let M be the set of all measurable sets in R, and let d be our semi-metric, show that (M, d) is complete:...
(5) Here is a fascinating equivalence for being a complete metric space that we will use later. Let (X,d) be a metric space. (b) ** (10 points) Show that the following are equivalent: • (X, d) is complete; • for every family of non-empty closed subsets Fo, F1, F2, ... of X such that F, 2 F12 F22... and limn700 diam( Fn) = 0, it holds that Nnen Fn = {a} for some a € X. (Hint: for the reverse...
* Exercise 10. Let M be a (non-empty) compact metric space and f: M → M a continuous map such that for every ε > 0 there exists x E M such that d(f(x), z) < E. Show that there exists y M such that f()y Hint: consider the map g: MR defined by g(x)=d(f(x),z).] [8 marks]
The question that is being asked is Question 3 that has a red
rectangle around it.
The subsection on Question 7 is just for the Hint to part d of
Question 3.
Question 3. Lul (X', d) be a metric space. A subsct ACX is said to be Gy if there exista a collection of open U u ch that A- , , Similarly, a subact BCis said to be F if there exista collection of closed sets {F}x=1 such...
New problems for 2020 1. A topological space is called a T3.space if it is a T, space and for every pair («,F), where € X and F(carefull), there is a continuous function 9 :X (0,1 such that f(x) 0 and f =1 on F. Prove that such a space has the Hausdorff Separation Property. (Hint: One point subsets are closed.] 2. Let X be topological space, and assume that both V and W are subbases for the topology. Show...