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In mathematics, the Fredholm alternative, named after Ivar Fredholm, is one of Fredholm's theorems and is a result in Fredholm theory. It may be expressed in several ways, as a theorem of linear algebra, a theorem of integral equations, or as a theorem on Fredholm operators. Part of the result states that a non-zero complex number in the spectrum of a compact operator is an eigenvalue. ==Linear algebra== If ''V'' is an ''n''-dimensional vector space and is a linear transformation, then exactly one of the following holds: #For each vector ''v'' in ''V'' there is a vector ''u'' in ''V'' so that . In other words: ''T'' is surjective (and so also bijective, since ''V'' is finite-dimensional). #. A more elementary formulation, in terms of matrices, is as follows. Given an ''m''×''n'' matrix ''A'' and a ''m''×1 column vector b, exactly one of the following must hold: #''Either:'' ''A'' x = b has a solution x #''Or:'' ''A''T y = 0 has a solution y with yTb ≠ 0. In other words, ''A'' x = b has a solution if and only if for any y s.t. ''A''T y = 0, yTb = 0 . 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「Fredholm alternative」の詳細全文を読む スポンサード リンク
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