Prove that A = {x : x € X and ƒÃ(x) = 0}. (iii) Suppose A and B are nonempty disjoint closed subsets of X. Use the function g = fĄ – ƒB to prove that there exist disjoint open sets U and V with ACU and B CV.

Advanced Engineering Mathematics
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Author:Erwin Kreyszig
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Chapter2: Second-order Linear Odes
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Could you teach me how to show (ii), (iii) in detail? 

Let A be a non-empty subset of a metric space (X,d) and x an element of X.
Define the distance from x to A as
d(x, A)
inf{d(x, a): a € A}.
(i) Prove that the function ƒÃ :
fA:
X → R, defined as ƒ₁(x) = d(x, A) satisfies
=
|ƒ^(x) - f^(y)] ≤<d(x, y) Vx, y ≤ X,
and that fд is continuous on X.
(ii) Prove that A = {x: xe X and f₁(x) = 0}.
(iii) Suppose A and B are nonempty disjoint closed subsets of X. Use the
function g = fA - ƒB to prove that there exist disjoint open sets U and V
with ACU and B C V.
Transcribed Image Text:Let A be a non-empty subset of a metric space (X,d) and x an element of X. Define the distance from x to A as d(x, A) inf{d(x, a): a € A}. (i) Prove that the function ƒÃ : fA: X → R, defined as ƒ₁(x) = d(x, A) satisfies = |ƒ^(x) - f^(y)] ≤<d(x, y) Vx, y ≤ X, and that fд is continuous on X. (ii) Prove that A = {x: xe X and f₁(x) = 0}. (iii) Suppose A and B are nonempty disjoint closed subsets of X. Use the function g = fA - ƒB to prove that there exist disjoint open sets U and V with ACU and B C V.
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