求lim(x趋于∞)x[ln(x+1)-lnx] 等于多少 求详解

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求lim(x趋于∞)x[ln(x+1)-lnx] 等于多少 求详解

求lim(x趋于∞)x[ln(x+1)-lnx] 等于多少 求详解
求lim(x趋于∞)x[ln(x+1)-lnx] 等于多少 求详解

求lim(x趋于∞)x[ln(x+1)-lnx] 等于多少 求详解
=lim x*ln[(x+1)/x]
=lim x*ln(1+1/x)
=lim ln[(1+1/x)^x]
=ln e
=1

x[ln(x+1)-lnx]
=ln[(x+1)/x]^x
=ln[(1+1/x)^x]
lim(x趋于∞)x[ln(x+1)-lnx]=lim(x趋于∞)ln[(1+1/x)^x]=e

解法一:原式=lim(x->∞){[ln(x+1)-lnx]/(1/x)}
=lim(x->∞){[1/(x+1)-1/x]/(-1/x²)} (0/0型极限,应用罗比达法则)
=lim(x->∞)[x/(x+1)]
=lim(x->∞)...

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解法一:原式=lim(x->∞){[ln(x+1)-lnx]/(1/x)}
=lim(x->∞){[1/(x+1)-1/x]/(-1/x²)} (0/0型极限,应用罗比达法则)
=lim(x->∞)[x/(x+1)]
=lim(x->∞)[1/(1+1/x)]
=1;
解法二:原式=lim(x->∞){xln[(x+1)/x]}
=lim(x->∞){ln[(1+1/x)^x]}
=ln{lim(x->∞)[(1+1/x)^x]}
=lne (应用重要极限lim(x->∞)[(1+1/x)^x]=e)
=1。

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