e^(-1/x^2)=1/[e^(1/x^2)]
若x→0,则x^2→0,1/x^2→∞
因为e>0,所以e^(1/x^2)→∞
则1/[e^(1/x^2)]→0
所以lim(x→0)e^(-1/x^2)=0