Question 1. Let f: XY and g: Y Z be two functions. Prove that (1) if go f is injective, then f is injective; (2) if go f is surjective, then g is surjective. Question 2. Prove or disprove: (1) The set X = {k € Z} is countable. (2) The set X = {k EZ,nЄN} is countable. (3) The set X = R\Q = {x ER2 countable. Q} (the set of all irrational numbers) is (4) The set X = {p.√2pQ} is countable. (5) The interval X = [0,1] is countable. Question 3. Let X = {f|f: N→ N}, the set of all functions from N to N. Prove that X is uncountable. Extra practice (not to be submitted). Question. Prove the following by induction. (1) For any nЄN, 1+3+5++2n-1 n². (2) For any nЄ N, 1+2+3++ n = n(n+1). Question. Write explicitly a function f: Nx N N which is bijective.

Algebra & Trigonometry with Analytic Geometry
13th Edition
ISBN:9781133382119
Author:Swokowski
Publisher:Swokowski
Chapter9: Systems Of Equations And Inequalities
Section9.5: Systems Of Linear Equations In More Than Two Variables
Problem 36E
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Question 1. Let f: XY and g: Y Z be two functions. Prove that
(1) if go f is injective, then f is injective;
(2) if go f is surjective, then g is surjective.
Question 2. Prove or disprove:
(1) The set X = {k € Z} is countable.
(2) The set X = {k EZ,nЄN} is countable.
(3) The set X = R\Q = {x ER2
countable.
Q} (the set of all irrational numbers) is
(4) The set X = {p.√2pQ} is countable.
(5) The interval X = [0,1] is countable.
Question 3. Let X = {f|f: N→ N}, the set of all functions from N to N. Prove
that X is uncountable.
Extra practice (not to be submitted).
Question. Prove the following by induction.
(1) For any nЄN, 1+3+5++2n-1 n².
(2) For any nЄ N, 1+2+3++ n = n(n+1).
Question. Write explicitly a function f: Nx N N which is bijective.
Transcribed Image Text:Question 1. Let f: XY and g: Y Z be two functions. Prove that (1) if go f is injective, then f is injective; (2) if go f is surjective, then g is surjective. Question 2. Prove or disprove: (1) The set X = {k € Z} is countable. (2) The set X = {k EZ,nЄN} is countable. (3) The set X = R\Q = {x ER2 countable. Q} (the set of all irrational numbers) is (4) The set X = {p.√2pQ} is countable. (5) The interval X = [0,1] is countable. Question 3. Let X = {f|f: N→ N}, the set of all functions from N to N. Prove that X is uncountable. Extra practice (not to be submitted). Question. Prove the following by induction. (1) For any nЄN, 1+3+5++2n-1 n². (2) For any nЄ N, 1+2+3++ n = n(n+1). Question. Write explicitly a function f: Nx N N which is bijective.
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