Example 2
Tag 06IO, permanent. Cite it as [Bourbaki, Tag 06IO].
Algebra, V, p. 22, § 4. Algebraically closed extensions
Let K be a field and an algebraically closed extension of K. If is the relative algebraic closure of K in , then by V, p. 20, Prop. 2, K is an algebraic closure of K. \* In particular the field of all algebraic numbers (V, p. 20, Ex. 2) is an algebraic closure of the field Q of rational numbers. \*
Bourbaki puts the proof directly after the statement, so what is above is the statement and its proof together.