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求limx→+∞(x^2/x^2-1)^x的极值
人气:274 ℃ 时间:2020-05-20 17:05:24
解答
[x^2/(x^2-1)]^x
=[x/(x+1)]^x*[x/(x-1)]^x
=[1-1/(x+1)]^(x+1)*[1+1/(x-1)]^(x-1)*[1+1/(x-1)]/[1-1/(x+1)]
当n→+∞时,[1-1/(x+1)]^(x+1)=1/e
[1+1/(x-1)]^(x-1)=e
[1+1/(x-1)]/[1-1/(x+1)]=1
故limx→+∞[x^2/(x^2-1)]^x=1
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