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In calculus, the racetrack principle describes the movement and growth of two functions in terms of their derivatives. This principle is derived from the fact that if a horse named Frank Fleetfeet always runs faster than a horse named Greg Gooseleg, then if Frank and Greg start a race from the same place and the same time, then Frank will win. More briefly, the horse that starts fast and stays fast wins. In symbols: :if for all , and if , then for all . or, substituting ≥ for > produces the theorem :if for all , and if , then for all . which can be proved in a similar way ==Proof== This principle can be proven by considering the function h(x) = f(x) - g(x). If we were to take the derivative we would notice that for x>0 : Also notice that h(0) = 0. Combining these observations, we can use the mean value theorem on the interval (x ) and get : Since x > 0 for the mean value theorem to work then we may conclude that f(x) - g(x) > 0. This implies f(x) > g(x). 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「Racetrack principle」の詳細全文を読む スポンサード リンク
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