Problem: Prove that every polynomial having real coefficients and odd degree has a real root
This is a problem from a chapter 5.4 'applications of connectedness' in a book 'Principles of Topology(by Croom)'
So you should prove by using the connectedness concept in Topology, maybe.
A field F is said to be perfect if every polynomial
over F is separable. Equivalently,
every algebraic extension of F is separable. Thus fields of
characteristic zero and
finite fields are perfect. Show that if F has prime characteristic p,
then F is perfect
if and only if every element of F is the pth power of some element
of F. For short we
write F = F p.
Does every polynomial equation have at least one real root?
a. Why must every polynomial equation of degree 3 have at least
one real root?
b. Provide an example of a polynomial of degree 3 with three
real roots. How did you find this?
c. Provide an example of a polynomial of degree 3 with only one
real root. How did you find this?
If F is a field and ?(?),?(?),h(?) ∈ ?[?]; and
h(?) ≠ 0.
a) Prove that [?(?)] = [?(?)] if and only if ?(?) ≡ ?(?)(???(
(h(?)).
b) Prove that congruence classes modulo h(?) are either disjoint
or identical.
An element a in a field F is called a primitive
nth root of unity if n is the smallest positive
integer such that an=1. For example, i is a primitive
4th root of unity in C, whereas -1 is not a primitive 4th root of
unity (even though (-1)4=1).
(a) Find all primitive 4th roots of unity in F5
(b) Find all primitive 3rd roots of unity in F7
(c) Find all primitive 6th roots of unity in F7...
Determine whether the polynomial is reducible or irreducible in
the given polynomial ring. Justify your answers.
(c) x^4 + 1 in Z5[x]
(e) 2x^3 − 5x^2 + 6x − 2 in Z[x]
(f) x^4 + 4x^3 + 6x^2 + 2x + 1 in Z[x]. Hint: Substitute x − 1
for x.
Use induction to prove
Let f(x) be a polynomial of degree n in Pn(R). Prove that for
any g(x)∈Pn(R) there exist scalars c0, c1, ...., cn such that
g(x)=c0f(x)+c1f′(x)+c2f′′(x)+⋯+cnf(n)(x), where f(n)(x)denotes the
nth derivative of f(x).