how do u do 6? F-'(C-D)= F-'(C)-F-'(D). 4. (10 points) In following questions a function f...
x+3 2x Define f(x) for all real numbers x = 0. Is f a one-to-one function? Prove or give a counterexample. (Note that the write-up of the proof or counterexample should only have a few of sentences.) If the co-domain is all real numbers not equal to 1, is f an onto function? Why or why not? (Note this problem does not require a full proof or formal counterexample, just an explanation.)
4) Let D be the set of all finite subsets of positive integers. Define a function (:2 - D as follows: For each positive integer n, f(n) =the set of positive divisors of n. Find the following f (1), f(17) and f(18). Is f one-to-one? Prove or give a counterexample.
Instruction: Do any 10 of the 14 questions. Each question is worth 10 points. (For each True/False question, if it is true, answer T and give reasons for your answer. If it is false, answer F and give a explicit counterexample or other explanation of why it is false.) 1) True or False: The set {x : x = : x = tany, y e [0,5)} is an compact subset of R, the set of all real numbers with the...
(5 pts each) Give example of an explicit function f in each of the following category with properly written domain D and range R such that (a) There exists a subset S of D with f-'[F(S)] + S (b) There exists a subset T of R with f[f-(T)] #T (11) (3+3+ 5 + 5 + 2) Define functional completeness. Show that x + y = (x + y) + (x + y), x · y = (x + x) +...
x?. Is f a one-to-one 3. (10 points) Define a function f on a set of real numbers by the rule f(x) correspondence (bijective)? If so find its inverse. Formally justify your answer.
Let f : A rightarrow D and g : B rightarrow C be functions. For each part, if the answer is yes, then prove it, otherwise give a counterexample. Suppose f is one-to-one (injective) and g is onto (surjective). Is go f one-to-one (injective)? Suppose f is one-to-one (injective) and g is onto (surjective). Is g f onto (surjective)? Suppose g is one-to one. Is g one-to-one? Suppose g f onto. Is g onto?
For each of the following functions, determine whether or not they are (i) one-to-one and i) onto. Justify your answers (a) f : R-{0} → R and f(x) = 3r-1/x (b) g : R _ {1} → R and g(x) = x + 1/(x-1) (c) l : S → Znon-reg and l(s) = number of 1's in s, for all strings s E S, where s is the set of all strings of O's and 1's. (d) 1 : S...
3. The identity function on the set X is denoted by ix and is defined by ix(x) = x for all x E X. It is known that f: X Y and g: Y X are functions. (a) Prove that if go f = ix, then f is one to one. (b) Give an example of f and g with gofrix but g is not one to one, (c) Prove that if go f = ix is onto, then g...
(10 points) Define a function on a set of real numbers by the rule f(x) = 2 Is ſ a one-to-one correspondence (bijective)? If so find its inverse. Formally justify your answer.
4. (4 points) Prove the truth or falsity of the following statements. To prove a statement true, give a formal argument (in cases involving implications among FD's, use Armstrong's Axiom System). To prove falsity, give a counterexample. 1. {A + B, DB → C} F{A+C} 2. {X+W, WZ+Y} F{XZ → WY} 3. {A D, B7C, F + B, CD + E|| F{AF → E} 4. Suppose R is a relation scheme and F a set of functional dependencies applicable to...