4. Prove that x – 15x³ + 10x² – 21x + 2021 is irreducible in Q[x]. -

Elements Of Modern Algebra
8th Edition
ISBN:9781285463230
Author:Gilbert, Linda, Jimmie
Publisher:Gilbert, Linda, Jimmie
Chapter7: Real And Complex Numbers
Section7.3: De Moivre’s Theorem And Roots Of Complex Numbers
Problem 20E
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Hi ,I need the proof of Question 4( not question 2)

4. Prove that a – 15a³ + 10a² – 21x + 2021 is irreducible in Q[x]. (Hint: Use Problem 2)
Transcribed Image Text:4. Prove that a – 15a³ + 10a² – 21x + 2021 is irreducible in Q[x]. (Hint: Use Problem 2)
2. Let D = Z[V–21] and N(z) := |z|?.
(a) Prove that z E D× if and only if N(z) = 1. Then deduce that D× = {-1,1}.
(b) Prove that V-21 is irreducible in D.
(c) Show that D/(V-21) is not an integral domain.
(d) Deduce that D is not a PID.
Transcribed Image Text:2. Let D = Z[V–21] and N(z) := |z|?. (a) Prove that z E D× if and only if N(z) = 1. Then deduce that D× = {-1,1}. (b) Prove that V-21 is irreducible in D. (c) Show that D/(V-21) is not an integral domain. (d) Deduce that D is not a PID.
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