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  2. Closed-form expression - Wikipedia

    en.wikipedia.org/wiki/Closed-form_expression

    The quadratic formula =. is a closed form of the solutions to the general quadratic equation + + =. More generally, in the context of polynomial equations, a closed form of a solution is a solution in radicals; that is, a closed-form expression for which the allowed functions are only n th-roots and field operations (+,,, /).

  3. Closure (mathematics) - Wikipedia

    en.wikipedia.org/wiki/Closure_(mathematics)

    In mathematics, a subset of a given set is closed under an operation of the larger set if performing that operation on members of the subset always produces a member of that subset. For example, the natural numbers are closed under addition, but not under subtraction: 1 − 2 is not a natural number, although both 1 and 2 are.

  4. Algebraically closed field - Wikipedia

    en.wikipedia.org/wiki/Algebraically_closed_field

    Such an extension is called an algebraically closed extension. Among all such extensions there is one and only one (up to isomorphism, but not unique isomorphism) which is an algebraic extension of F; [3] it is called the algebraic closure of F. The theory of algebraically closed fields has quantifier elimination.

  5. Algebraic closure - Wikipedia

    en.wikipedia.org/wiki/Algebraic_closure

    In mathematics, particularly abstract algebra, an algebraic closure of a field K is an algebraic extension of K that is algebraically closed. It is one of many closures in mathematics. Using Zorn's lemma [ 1 ] [ 2 ] [ 3 ] or the weaker ultrafilter lemma , [ 4 ] [ 5 ] it can be shown that every field has an algebraic closure , and that the ...

  6. Closed graph theorem (functional analysis) - Wikipedia

    en.wikipedia.org/wiki/Closed_graph_theorem...

    In mathematics, particularly in functional analysis, the closed graph theorem is a result connecting the continuity of a linear operator to a topological property of their graph. Precisely, the theorem states that a linear operator between two Banach spaces is continuous if and only if the graph of the operator is closed (such an operator is ...

  7. Liouville's theorem (differential algebra) - Wikipedia

    en.wikipedia.org/wiki/Liouville's_theorem...

    Nonelementary integral – Integrals not expressible in closed-form from elementary functions; Risch algorithm – Method for evaluating indefinite integrals; Tarski's high school algebra problem – Mathematical problem; Transcendental function – Analytic function that does not satisfy a polynomial equation

  8. Closed graph theorem - Wikipedia

    en.wikipedia.org/wiki/Closed_graph_theorem

    The closed graph theorem is an important result in functional analysis that guarantees that a closed linear operator is continuous under certain conditions. The original result has been generalized many times. A well known version of the closed graph theorems is the following.

  9. Inscribed square problem - Wikipedia

    en.wikipedia.org/wiki/Inscribed_square_problem

    The inscribed square problem, also known as the square peg problem or the Toeplitz' conjecture, is an unsolved question in geometry: Does every plane simple closed curve contain all four vertices of some square? This is true if the curve is convex or piecewise smooth and in other special cases. The problem was proposed by Otto Toeplitz in 1911. [1]