y=x^(1/3)
y'=(1/3)*x^(-2/3)
=1/[3x^(3/2)]
而在x=0处的导数即
y'|(x=0)
=1/[3*0^(3/2)]
=1/0,(分式无意义)
∴y=f(x)在x=0处的导数不存在.