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问题: 极限问题1

解答:

[(x+2a)/(x-a)]^(x/3)
=[(1+2a/x)/(1-a/x)]^(x/3)
={(1+2a/x)/(1-a/x)]^(x/a)}^(a/3)
依照基本极限,x->∞:lim(1+m/x)^x=e^m
所以x->∞:lim(1+2a/x)^(x/a)=e^2
,,,,,,,,,,lim(1-a/x)^(x/a)=e^(-1)
因此,原式=[e^2/e^(-1)]^(a/3)=(e^3)^(a/3)=e^a