等价无穷小
=(x^3-1)/(x^2-1)
=(x-1)(x^2 x 1)/(x-1)(x 1)
=(x^2 x 1)/(x 1)
代入x=1
得3/2
也可以洛必达法则
=cos(x^3-1)(3x^2)/2x
=cos(x^3-1)(3x)/2
代入x=1
的3/2