令 x-1=t,t-->0
lim (x-->+1)（(x^2-1)/(x-1))e^1/(x-1)
=(x-->+1)（(x+1)e^1/(x-1)
=lim (t-->+0)（t+2)e^1/t
=+∞
lim (x-->1-)（(x^2-1)/(x-1))e^1/(x-1)
=(x-->1-)（(x+1)e^1/(x-1)
=lim (t-->-0)（t+2)e^1/t
=0