13. Explain how to determine the maximum and minimum of f(x)=12x-x³ on the interval x[-3,5]. You don't actually need to determine the solution. 14. Sketch the graph of f(x)=-4x³ +18.x² +3 by calculating: a. The y-intercept b. Minimum and maximum points (include intervals of increase and decrease c. Points of inflection (include intervals of concavity) d. Sketch the graph (given the x-intercept = 4.5