1st and second derivative test:

Find from the 1st derivative where the interval is increasing/decreasing. And find also the critical points.

Find from the 2nd derivative any points of inflection of the graph of the function and determine where the graph is concave upward and concave downward.

Support your answer by plotting in the same window the graph of the function and the inflectional tangents.

$\displaystyle f(x) = x^4 - 2x^3$

Really appreciating any help