求limx^2[1/(x-1)-1/(x+1)],x→无穷的极限

Question

求limx^2[1/(x-1)-1/(x+1)],x→无穷的极限

Answer 1

原式=limx^2[2/(x^2-1)]
=2limx^2/(x^2-1)
=2lim1/(1-1/x^2)(分子分母同除以x^2)
=2*1=2