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In algebra, a nested radical is a radical expression (one containing a square root sign, cube root sign, etc.) that contains (nests) another radical expression. Examples include : which arises in discussing the regular pentagon, and more complicated ones such as : == Denesting nested radicals == Some nested radicals can be rewritten in a form that is not nested. For example, : : : Squaring both sides of this equation yields: : This can be solved by finding two numbers such that their sum is equal to ''a'' and their product is ''b2c/4'', or by equating coefficients of like terms—setting rational and irrational parts on both sides of the equation equal to each other. The solutions for ''e'' and ''d'' can be obtained by first equating the rational parts: : which gives : : For the irrational parts note that : and squaring both sides yields : By plugging in ''a'' − ''d'' for ''e'' one obtains : Rearranging terms will give a quadratic equation which can be solved for ''d'' using the quadratic formula: : : Since ''a'' = ''d+e'', the solution ''e'' is the algebraic conjugate of ''d''. If we set : then : However, this approach works for nested radicals of the form if and only if is a rational number, in which case the nested radical can be denested into a sum of surds. In some cases, higher-power radicals may be needed to denest the nested radical. 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「nested radical」の詳細全文を読む スポンサード リンク
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