Created the Abstract Algebra theorems and definitions cheat sheet

part-4/chapters/chapter-20/the-fundamental-theorem-of-field-theory.tex

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+\section{The Fundamental Theorem of Field Theory}
+
+\begin{definition}[Extension Field]
+	A field $\E$ is an \textit{extension field} of a field $\F$ if $\F \subseteq \E$ and the operations of $\F$ are those of $\E$ restricted to $\F$.
+\end{definition}
+
+\begin{theorem}[Fundamental Theorem of Field Theory (Kronecker's Theorem, 1887)]
+	Let $\F$ be a field and let $f(x)$ be a nonconstant polynomial in $\F[x]$. Then there is an extension field $\E$ of $\F$ in which $f(x)$ has a zero.
+\end{theorem}