eisenstein criterion for irreducibility
Show that the following polynomials are irreducible over Q. (a) (8 points) f(1) = 5.rº –...
Preview Activity 14.1. In previous investigations, we defined irreducible polynomials and showed that irreducible polynomials in polynomial rings over fields play the same role as primes play in Z. In this investigation we will explore some methods to determine when a polynomial is irreducible, with a special emphasis on polynomials with coefficients in C, R, and Q. To begin, we will review the definition and a simple case. Let F be a field. (a) Give a formal definition of what...
Rings and fields- Abstract Algebra 2. (a) (6 points) Let f (x) be an n over a field F. Let irreducible polynomial of degree g() e Fx be any polynomial. Show that every irreducible factor of f(g()) E Flx] has degree divisible by n (b) (4 points) Prove that Q(2) is not a subfield of any cyclotomic field over Q. 2. (a) (6 points) Let f (x) be an n over a field F. Let irreducible polynomial of degree g()...
Determine whether the following polynomials are irreducible in Q[x]. (i) f(x) = 3x2 – 7x – 5 (ii) f(x) = 2x3 – x – 6 (iii)f(x) = x3 + 6x2 + 5x + 25
Write the polynomial f(x) as a product of irreducible polynomials in the given ring. Explain in each case how you know the factors are irreducible. 1) f(x) -x* + 2x2 +2x 2 in Z3[x]. 2) f(x)4 + 2x3 + 2x2 +x + 1 in Z3[x]. 3) f(x) 2x3-x2 + 3x + 2 in Q[x] 4) f(x) = 5x4-21x2 + 6x-12 in Q[x)
Part D,E,F,G 10. Let p(x) +1. Let E be the splitting field for p(x) over Q. a. Find the resolvent cubic R(z). b. Prove that R(x) is irreducible over Q. c. Prove that (E:Q) 12 or 24. d. Prove: Gal(E/Q) A4 or S4 e. If p(x) (2+ az+ b)(a2 + cr + d), verify the calculations on page 100 which show that a2 is a root of the cubic polynomial r(x)3-4. 1. f. Prove: r(x) -4z 1 is irreducible in...
6. One root of the polynomial f(x) = 2x5 – 23x4 + 76x3 – 9x2 – 246c +234 over C is 5 - i. (a) Write f(x) as a product of irreducible polynomials in Q[x]. Show your work. (b) Write f(x) as a product of irreducible polynomials in R[x]. Show your work. (c) Write f(x) as a product of irreducible polynomials in C[x]. Show your work.
Theorem 14.7. If f(x) € R[x] is an irreducible polynomial, then deg(f(x)) is either 1 or 2. We can determine which quadratic polynomials in R[x] are irreducible by using the quadratic formula and checking for real roots. Activity 14.8. Factor f(x) = 2 – 4.x in R[2] into a product of irreducible polynomials in R[2].
4. (a) Prove that if f(x) E Q[x] is irreducible in R[x], then it is irreducible in Q[x]. Is the converse of this statement true? Explain why or why not. (b) Prove that if f(x) E Q[x] is reducible in Q[x], then it is reducible in R[x]. Is the converse of this statement true? Explain why or why not.
Polynomial over the Fields: a) If p(x) an element of F[x] is not irreducible, then there are at least two polynomials g(x) and h(x), neither which is a constant, such that p(x)=g(x)h(x). Explain b) Use problem a to prove: If p(x) is not irreducible, then p(x)=j(x)k(x), where both j(x) and k(x) are polynomials of lower degree than p(x).
Fields Suppose F=Q, K=Q(sqrt (3)) and E=Q(sqrt(12)). Find the minimum polynomials h(x) for sqrt(3) and g(x) for sqrt(12) over Q. K and E are in the same field. Explain why these two polynomials have no roots in common.