Question 1123975
"Critical values"?



{{{df/dx=-15x^2+15x^4}}}


{{{15x^4-15x^2=0}}}

{{{x^4-x^2=0}}}

{{{x^2(x^2-1)=0}}}

{{{x^2(x-1)(x+1)=0}}}


The local extreme points are at x of -1, 0, and 1.


Maximum at x=-1, minimum at x=1.
Inflexion which is not an extreme point for x at 0.


You may be able to use second-derivative to help with these.