3. Let X and Y be countably infinite sets. (a) Prove: If X and Y are...
Prove that a disjoint union of any finite set and any countably infinite set is countably infinite. Proof: Suppose A is any finite set, B is any countably infinite set, and A and B are disjoint. By definition of disjoint, A ∩ B = ∅ Then h is one-to-one because f and g are one-to one and A ∩ B = 0. Further, h is onto because f and g are onto and given any element x in A ∪...
A . Prove that Problem 4. (2 points) Let A and B be two sets. Suppose that A B = B A = B. Problem 5. (optional but recommended). Show that the set X = {(...) 21: sequences of O's and I's is not countably infinite. Hint: think of a natural function between X and P(N). € {0,1}} of infinite
From the class Introduction to Abstract Algebra on the section of countable and uncountable sets 3. Let X and Y be two nonempty finite sets. Let F(X, Y) denote the set of all function from X to Y. Is this set finite, countably infinite, or uncountable? Prove your answer
Q4 Let F denote a countably infinite set of functions such that each f; e F is a function from Z+ to R+, and let R be a homogeneous binary relation on F where R = {(fa, fb) | fa(n) € (fo(n))}. Prove that R is a reflexive relation. In your proof, you may not use a Big-12, Big-0, or Big- property to directly justify a relational property with the same name; instead, utilize the definition of Big-12, Big-O, and...
Write a formal proof to prove the following conjecture to be true or false. If the statement is true, write a formal proof of it. If the statement is false, provide a counterexample and a slightly modified statement that is true and write a formal proof of your new statement. Conjecture: 15. (12 pts) Let h: R + RxR be the function given by h(x) = (x²,6x + 1) (a) Determine if h is an injection. If yes, prove it....
Let X, Y, Z be random variables. Prove or disprove the following statements. (That means, you need to either write down a formal proof, or give a counterexample.) (a) If X and Y are (unconditionally) independent, is it true that X and Y are conditionally indepen- dent given Z? (b) If X and Y are conditionally independent given Z, is it true that X and Y are (unconditionally) independent?
please let words clear, thanks 7. Recall that the notation alb is read as "a divides b" and means that there is some integer x such that b ax. Now consider the following sentence: a e a) Write the negation of the sentence above in symbols, simplifying whenever b) The ORIGINAL sentence above is false. Provide a counterexample that demonstrates this and explain why it is a counterexample. Hint: a counterexample for this statement would be a proof of its...
(3 + 3 = 6 pts.) Prove or disprove the following statements. If you are proving a statement, then give proper reasoning. If you are disproving a statement, then it is enough to give an example which demonstrates that the statement is false. i. If A and B are two n x n matrices, then (A + B)2 = A + 2AB + B2. ii. Let A be a nxn matrix and let I be the n x n identity...
(1) Let X and Y be sets. Let f be a function from X to Y, (a) IF BEY, recall that F-'(B) = {xeX \flyeBX(y,x) ef-)}. Prove that f'(B)={xeX | fk)e B}. (hint: Reprember that even though t is a thought is a function, the relation f may well not be itself a function.) Al b) Let {B; \je J} be an inbred family of subsets of Y. Prove that of "b) = f'(21B;).
16 pts) PROBLEM 21. Let f:X →Y be a function, let Xi, X2SX andlet Yi, ½SY. ) Write down the definitions of f(Xi) and f (Y 。ín½) = f-'(%) nf-106). (ii) Prove that (ii) Prove that f(XinX)(xnf(xa) (i) Find a counterexample to the statement (xinx) J(x)n(X) Do not show how you found the right ideas. Present detailed and carefully set out definitions and proofs only END of PROBLEM 21 16 pts) PROBLEM 21. Let f:X →Y be a function, let...