Applying the First Derivative Test In Exercises 23-56, (a) find the critical numbers of f, if any, (b) find the open intervals on which the function is increasing or decreasing, (c) apply the First Derivative Test to identify all relative extrema, and (d) use a graphing utility to confirm your results. 27. f (x) = -7x3 + 21x + 3 28. f(x) =x3 - 6x2+ 15 - 1)2 12/3 x - 5 x = 2x + X 9 43. f(x) = 14 2 x. >0 ver - 3 47. f(x) = 4(x - arcsin x)