So the question, based on the given function in your question, is asking to calculate on which value of F is increasing and decreasing and base on my own research and calculation, I would say that the answer would be (5, -621).
(-inf,0) concave up
(0,inf) concave up, -5,5) concave down, decreasing (-inf,-5), increasing (-5,0), decreasing (0,5), increasing (5,inf) and f(5) = (5)^4 - 50(5)^2 + 4 = (5,-621) MIN. I hope this would help
