Mathematics

Problem

Let

f

be a twice–differentiable function whose first derivative is

f'(x)=x^{3}-6x

. At which

x

–value(s) does the graph of

f

have a point of inflection? a)

x=\pm 2

x=\pm\sqrt{2}

x=0

only d)

x=0,\,\pm\sqrt{6}