Prove the following:
(a) Let A be a ring and B be a field. Let f : A → B be a
surjective homomorphism from A to B. Then ker(f) is a maximal
ideal.
(b) If A/J is a field, then J is a maximal ideal.
Prove
1. Let f : A→ B and g : B → C . If g 。 f is one-to-one, then f
is one-to-one.
2. Equivalence of sets is an equivalence relation (you may use
other theorems without stating them for this one).
Exercise 4. Let ≥ be a rational, monotone and continuous
preference on R2 +. Suppose that ≥ is such that there is at least
one strict preference statement, i.e. there exists two bundles x
and y in R2 + such that x>y.
(a) Is there a discontinuous utility representation of ≥ ?
Justify your answer.
(b) Would your answer change if if we didn’t have at least one
strict preference statement? Justify your answer.
I don't know where my professor...
Let f: X→Y be a map with A1, A2⊂X and
B1,B2⊂Y
(A) Prove
f(A1∪A2)=f(A1)∪f(A2).
(B) Prove
f(A1∩A2)⊂f(A1)∩f(A2).
Give an example in which equality fails.
(C) Prove
f−1(B1∪B2)=f−1(B1)∪f−1(B2),
where f−1(B)={x∈X: f(x)∈B}.
(D) Prove
f−1(B1∩B2)=f−1(B1)∩f−1(B2).
(E) Prove
f−1(Y∖B1)=X∖f−1(B1).
(Abstract Algebra)
1. What is a monotone class?
2.Prove that every algebra or field is a monotone class
Proof that
1. show that the intersection of any collection of algebra or field
on sample space is a field
2. Union of field may not be a field