x/2-1

题目

x/2-1
lim(1-2/x)
x→∞

答案

令t=x/2-1
(t+1)=x/2
2/x=1/(t+1)
lim (1-1/(t+1))^t=lim(1+(1/-(t+1)))^[-(t+1)*(-1)]*(1+(1/-(t+1)))^(-1)
-(t+1)->∞
=1/e