即证明lim(n→∞)n^2q^n=0因为00)任意给定正数a，取N=max{4,[12/(ah^3)]+1}当n>=N时，|n^2q^n-0|=n^2/(1+h)^n=4)=1/n*1/(1-1/n)*1/(1-2/n)*3/h^3<1/n*1/(1/2)*1/(1/2)*3/h^3 (n>=4)=1/n*12/h^312/(ah^3))所以极限为0
