1. Prove that the function f: X → Y is injective if and only if it...
8. Prove the following: a. A function, f: X Y, is injective if and only if If-2013 1 for each y EY b. A function, f:X + Y, is surjective if and only if \f-1(y) 2 1 for each y E Y c. A function, f:X → Y, is bijective if and only if \f-(y)= 1 for each y E Y
Problem 1. (2 credits) Let f: X +Y. Prove that f is injective if and only if there exists a function g: Y → X such that go f = ldx.
Let h : X −→ Y be defined by h(x) := f(x) if x ∈ F g −1 (x) if x ∈ X − F Now we must prove that h is injective and bijective. Starting with injectivity, let x1, x2 ∈ X such that h(x1) = h(x2). Assume x1 ∈ F and x2 ∈ X −F. Then h(x1) = f(x1) ∈ f(F) and h(x2) = g −1 (x2) ∈ g −1 (X − F) = Y...
Prove If the functions are injective, surjective, or bijective. You must prove your answer. For example, if you decide a function is only injective, you must prove that it is injective and prove that it is not surjective and that it is not bijective. Similarly, if you claim a function is only surjective, you must prove it is surjective and then prove it is not injective and not bijective. - Define the function g: N>0 → N>0 U {0} such that g(x) = floor(x/2). You may use the fact that...
Let X and Y be any sets and let F be any one-to-one (injective) function from X to Y . Prove that for every subset A ⊂ X: (a) (10 points) A ⊂ F^(−1) (F(A)). (b) (10 points) F ^(−1) (F(A)) ⊂ A
2 Functions a. A function f : A-B is called injective or one-to-one if whenever f(x)-f(y) for some x, y E A then x = y. That is Vz, y A f(x) = f(y) → x = y. Which of the following functions are injective? In each case explain why or why not i. f:Z-Z given by f() 3r +7 (1 mark ii. f which maps a QUT student number to the last name of the student with that student...
4. Let X and Y be any sets and let F be any one-to-one (injective) function from X to Y. Prove that for every subset A CX: (a) (10 points) AC F-(F(A)). (b) (10 points) F-1(F(A)) C A.
1. Let A, B be two non-empty sets and f: A + B a function. We say that f satisfies the o-property if VC+0.Vg, h: C + A, fog=foh=g=h. Prove that f is injective if and only if f satisfies the o-property.
23. (a) Show that a function f : X → Y is a surjection if and only if there is a funct io On g : Y → X such that fog = idy. (b) Show that a function : X → Y with nonempty domain X is an injection if and only if there is a function g : Y → X such that g o f-idx. How does this result break down if X = φ? (c) Show...
1 Let f (t), g(t) be a continuous function on some interval I, and to e I. Prove that the initial value problem y'(t) f(t)y + g(t)y2, y(to) zo has a unique and continuous solution φ(t) on a small interval containing to, φ(t) satisfies the initial condition φ(to) = to. 1 Let f (t), g(t) be a continuous function on some interval I, and to e I. Prove that the initial value problem y'(t) f(t)y + g(t)y2, y(to) zo has...