For the function f (x) = -3.x3 +x- 2.x, (a) List the x values where d'f = 0 . dx2 (b) Are all of these values abscissas of inflection points?d-f (a) = 0 at x = + dx2 (b) The value(s) in a. Select are abscissas of inflection points are not abscissas of inflection points