For each function in below Problems find the relative maxima, relative minima, horizontal points of inflection, and sketch the graph check your graph with a graphing utility.
1. y = 1/3x3 - x2 + x 1
2. y = 1/4x4 - 2/3x3 + 1/2x2 -2
3. y = 1/3x3 + x2 - 24x + 20
4. C(x) = x3 - 3/2x2 - 18x + 5
5. y = 3x5 - 5x3 + 1