Given points xn and x in Rd
prove that:
xn→x, i.e., for each ε >0 there exists an integer N >0 such that n ≥ N ⇒ ‖x−xn‖< ε.
and
For each ε >0 there exists an integer N >0 such that n ≥ N ⇒ ‖x−xn‖ ≤ ε
are equivalent.


Given points xn and x in Rd prove that: xn→x, i.e., for each ε >0 there...
A metric space (X, d) is totally bounded if, given
ε>0, there exists a finite subset =
of X, called an ε-net, such that for each x∈X there
exists
∈
such that d(x,)
< ε. Prove that if Y is a subset of a totally bounded space X
then, given ε>0, the subset Y has an ε-net and
therefore Y is also totally bounded.
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Where n is any positive integer, do the following: A. For ε > 0, prove that an converges to a limit of 4 by using the formal definition of convergence of a sequence to a limit, showing all work. 1. Justify each step as part of your proof in A.
Please help! Only answer
questions 5-8!
Definition 0.1. A sequence X = (xn) in R is said to converge to x E R, or x is said to be a limit of (xif for every e > 0 there exists a natural number Ke N such that for all n > K, the terms Tn satisfy x,n - x| < e. If a sequence has a limit, we say that the sequence is convergent; if it has no limit, we...
If (xn)– is a convergent sequence with limn700 Xn = 0 prove that x1 + x2+...+xn = 0. n lim n +00
the set of compactly supported sequences is defined by c00 = {{xn} : there exists some N ≥ 0 so that xn = 0 for all n ≥ N } Prove that for 1 ≤ p ≤ ∞ the metric space (c00, dp) is not complete.
the set A ⊆ L^2 by A = { {xn} ∈ L^ 2 : X∞ n=0 (1 + n)|xn| 2 ≤ 1 } Prove A is totally bounded, and compact.
3. Suppose X is a metric space with a sequence of points Xn e X with the property that for each n + m we have d(Xn, Xm) = 1. Prove that no subsequence of xn converges, and that therefore X is not compact. Hint: You could use the previous problem.
Q3 (Prove that P∞ k=1 1/kr < ∞ if r > 1) . Let
f : (0,∞) → R be a twice differentiable function with f ''(x) ≥ 0
for all x ∈ (0,∞).
(a) Show that f '(k) ≤ f(k + 1) − f(k) ≤ f '(k + 1) for all k ∈
N.
(b) Use (a), show that Xn−1 k=1 f '(k) ≤ f(n) − f(1) ≤ Xn k=2 f
'(k).
(c) Let r > 1. By finding...
2. Let Xn,n0,1,2,... denote a biased random walk given by Xo 0 and Xn+1 Xn + YTHI, where (X } are 1.1.d. random variables with N(-1,1) distribution. Show that Mn X22n Xn (n -1) is a martingale.
2. Let Xn,n0,1,2,... denote a biased random walk given by Xo 0 and Xn+1 Xn + YTHI, where (X } are 1.1.d. random variables with N(-1,1) distribution. Show that Mn X22n Xn (n -1) is a martingale.
5. Use induction to prove the following for x,y EQ and n, mEN. (c) xn = 0 iff x = 0 (d) If x 〉 y 〉 0, then xn 〉 yn 〉 0