All but one of the functions is differentiable for all real

Last updated: 8/13/2022

All but one of the functions is differentiable for all real values of x. Which function is not differentiable for at least one real value of x? f(x)=x² +1 g(x) = 1/x² +1 h(x) = |x| j(x) = x³ - 3x