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Position: Home > Articles > The Limit Analysis on Integrated Function f(x) of Abnormal integral from n=a to +∞(f(x)dx) Journal of Yangtze University(Natural Science Edition)Agricultural Science Volumn 2011 (9) 4-5+13

无穷限积分integral from n=a to +∞ (f(x)dx)中被积函数f(x)的渐近分析

作  者:
熊骏;曾鹏
单  位:
沙市第九中学;长江大学信息与数学学院
关键词:
无穷限积分;被积函数;渐近分析
摘  要:
讨论了收敛的无穷限积分integral from n=a to +∞ (f(x)dx)中被积函数limx→+∞f(x)=0的充分条件以及在一些条件下limf(x)=0的速度,得到了如下结果:若无穷限积分integral from n=a to +∞ (f(x)dx)收敛且极限limx→+∞f(x)存在,则limx→+∞f(x)=0;若无穷限积分integral from n=a to +∞ (f(x)dx)收敛,且f(x)在[a,+∞)上一致连续,则limx→+∞f(x)=0;若无穷限积分∫+∞af(x)dx收敛且f(x)在[a,+∞)上单调,则limx→+∞xf(x)=0,即f(x)=o1(x),x→+∞;若无穷限积分integral from n=a to +∞ (f(x)dx)收敛(p>0),且f(x)在[a,+∞)上单调,则limxp+1 f(x)=0。
译  名:
The Limit Analysis on Integrated Function f(x) of Abnormal integral from n=a to +∞(f(x)dx)
作  者:
XIONG Jun (Yangtze University,Jingzhou 434023)ZENG Peng (Shashi 9th Middle School,Jingzhou 434000)
关键词:
abnormal integration;integrated function;limit analysis
摘  要:
In this paper,the sufficient conditions about limx→+∞f(x)=0 and the limits of functions in abnormal integration are discussed,some results are obtained:if integral from n=a to +∞(f(x)dx) converges to a limit and limx→+∞f(x) exists,then limx→+∞f(x)=0;when integral from n=a to +∞(f(x)dx) converges to a limit,and f(x) is continuous uniformly on [a,+∞),then limx→+∞xf(x)=0,says f(x)=o(1/x),x→+∞;if integral from n=a to +∞(f(x)dx) converges to a limit(p>0),and f(x) is monotonous on [a,+∞),then limx→+∞xp+1f(x)=0.

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