Let X, Y and Z be sets. Let f : X → Y and g :...
Let X, Y and Z be sets. Let f : X → Y and g : Y → Z functions.
(a) (3 Pts.) Show that if g ◦ f is an injective function, then f is
an injective function. (b) (2 Pts.) Find examples of sets X, Y and
Z and functions f : X → Y and g : Y → Z such that g ◦ f is
injective but g is not injective. (c) (3 Pts.) Show that...
Let f : A → B and g : B → C. For each statement below...
Let f : A → B and g : B → C. For each statement below either
prove it or construct f, g, A, B, C which show that the statement
is false.
(a) If g ◦ f is surjective, then g is surjective.
(b) If g ◦ f is surjective, then f is surjective.
(c) If g ◦ f is injective, then f and g are injective
Part II
True or false:
a. A surjective function defined in a finite set X
over...
Part II
True or false:
a. A surjective function defined in a finite set X
over the same set X is also BIJECTIVE.
b. All surjective functions are also
injective functions
c. The relation R = {(a, a), (e, e), (i, i), (o, o), (u, u)} is
a function of V in V if
V = {a, e, i, o, u}.
d. The relation in which each student is assigned their age is a function.
e. A bijective function defined...
Let f:A→B and g:B→C be maps. Prove that if g◦f is a bijection,
then f is...
Let f:A→B and g:B→C be maps. Prove that if g◦f is a bijection,
then f is injective and g is surjective.*You may not use, without
proof, the result that if g◦f is surjective then g is surjective,
and if g◦f is injective then f is injective. In fact, doing so
would result in circular logic.
For an abelian group G, let tG = {x E G: x has finite order}
denote...
For an abelian group G, let tG = {x E G: x has finite order}
denote its torsion subgroup.
Show that t defines a functor Ab -> Ab if one defines t(f) =
f|tG (f restricted on tG) for every homomorphism f.
If f is injective, then t(f) is injective.
Give an example of a surjective homomorphism f for which t(f)
is not surjective.
Let S = {A, B, C, D, E, F, G, H, I, J} be the set...
Let S = {A, B, C, D, E, F, G, H, I, J} be the set consisting of
the following elements:
A = N, B = 2N , C = 2P(N) , D = [0, 1), E = ∅, F = Z × Z, G = {x
∈ N|x 2 + x < 2}, H = { 2 n 3 k |n, k ∈ N}, I = R \ Q, J =
R.
Consider the relation ∼ on S given...