lim(x->∞) [x^2(1+1/x^2)]/[x^2(2+2/x-1/x^2)]
=lim(x->∞) (1+1/x^2)/(2+2/x-1/x^2)
=(1+0)/(2+0-0)
=1/2低级失误……已经做出来了……Ok！