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Polynomial function theorems for zeros are a set of theorems aiming to find (or determine the nature of) the polynomial remainder theorem: * Factor theorem * Descartes' rule of signs * Gauss–Lucas theorem * Rational zeros theorem * Bounds on zeros theorem also known as the ''boundedness theorem'' * Intermediate value theorem * Complex conjugate root theorem * Properties of polynomial roots ==Background== A polynomial function is a function of the form :, where are complex numbers and . If , then is called a ''zero'' of . If is real, then is a ''real zero'' of ; if is imaginary, the is a ''complex zero'' of , although complex zeros include both real and imaginary zeros. The fundamental theorem of algebra states that every polynomial function of degree has at least one complex zero. It follows that every polynomial function of degree has exactly complex zeros, not necessarily distinct. * If the degree of the polynomial function is 1, i.e., , then its (only) zero is . * If the degree of the polynomial function is 2, i.e., , then its two zeros (not necessarily distinct) are . A degree one polynomial is also known as a linear function, whereas a degree two polynomial is also known as a quadratic function and its two zeros are merely a direct result of the quadratic formula. However, difficulty rises when the degree of the polynomial, ''n'', is higher than 2. There is a cubic formula for a cubic function (a degree three polynomial) and there is a quartic formula for a quartic function (a degree four polynomial), but they are very complicated. There is no general formula for a polynomial function of degree 5 or higher (see Abel–Ruffini theorem). 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「Polynomial function theorems for zeros」の詳細全文を読む スポンサード リンク
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