(1-1/x)^x=[(x-1)/x]^x=[x/(x-1)]^(-x)=[1+1/(x-1)]^(-x)=1/[1+1/(x-1)]^(x)=1/[1+1/(x-1)]^(x-1)*[1+1/(x-1)]当x趋于正无穷时,1/[1+1/(x-1)]^(x-1)*[1+1/(x-1)]=1/[1+1/(x-1)]^(x-1)=1/e