=[(1-2/x)^(-x/2)]^[(x/2-1)/(-x/2)]
=e^[-(x/2-1)*(2/x)]
=e^[-(x-2)/2*(2/x]
=e^[-(x-2)/x]
=e^(-1)
=1/e
lim->无穷大（1-2/x)^(x/2-1)
=[(1-2/x)^(-x/2)]^[(x/2-1)/(-x/2)]
=e^[-(x/2-1)*(2/x)]
=e^[-(x-2)/2*(2/x]
=e^[-(x-2)/x]
=e^(-1)
=1/e