# I What is Kronecker's theorem/lemma for root solutions?

#### swampwiz

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#### fresh_42

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If we had more than one zero in a field extension, then there would be a field in between with those zeros and no others of degree greater than two. But the total degree of the splitting field is prime and the degree of the smaller field would be a divisor of that prime. Thus there can only be one zero or already all.

#### swampwiz

If we had more than one zero in a field extension, then there would be a field in between with those zeros and no others of degree greater than two. But the total degree of the splitting field is prime and the degree of the smaller field would be a divisor of that prime. Thus there can only be one zero or already all.
Hi, do you have link that discusses the proof for this?

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2018 Award

#### sysprog

The textbook, A First Course in Abstract Algebra: Rings, Groups, and Fields, Third Edition, by Marlow Anderson and Todd Feil, has a proof of Kronecker’s Theorem, and uses and discusses it extensively.

Summary for Chapter 48 Solving Polynomials by Radicals:
In this chapter we prove that if a polynomial over a subfield of the complex numbers can be solved by radicals, then the Galois group of its splitting field over the base field is necessarily a solvable group. We can then easily exhibit a fifth degree polynomial over the rational numbers that cannot be solved by radicals.​

"What is Kronecker's theorem/lemma for root solutions?"

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