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In mathematics, a dependence relation is a binary relation which generalizes the relation of linear dependence. Let be a set. A (binary) relation between an element of and a subset of is called a ''dependence relation'', written , if it satisfies the following properties: * if , then ; * if , then there is a finite subset of , such that ; * if is a subset of such that implies , then implies ; * if but for some , then . Given a ''dependence relation'' on , a subset of is said to be ''independent'' if for all If , then is said to ''span'' if for every is said to be a ''basis'' of if is ''independent'' and ''spans'' Remark. If is a non-empty set with a dependence relation , then always has a basis with respect to Furthermore, any two bases of have the same cardinality. ==Examples== * Let be a vector space over a field The relation , defined by if is in the subspace spanned by , is a dependence relation. This is equivalent to the definition of linear dependence. * Let be a field extension of Define by if is algebraic over Then is a dependence relation. This is equivalent to the definition of algebraic dependence. 抄文引用元・出典: フリー百科事典『 ウィキペディア(Wikipedia)』 ■ウィキペディアで「Dependence relation」の詳細全文を読む スポンサード リンク
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