答：例子1是正确的解答过程例子4解答错误，应该要提取-x才对lim[-x√(4+1/x-1/x^2)-x+1]/[-x√(1+sinx/x^2]=lim[√(4+1/x-1/x^2)+1-1/x]/√(1+sinx/x^2)=(2+1)/1=3才对的直接用等价也可以：lim(2|x|-x|)/|x|=lim(2|x|+|x|)/|x|=3
