Find the critical points of the function f (x) = $x3 + x2 -15x -1. Use the first derivate test to classify the critical points as local maximum, local minimum or neither. Be sure to include derivative step and interval chart as shown in the example. Derivative: Critical numbers: Interval: Intervals Chart: Interval Test Value Sign of f '(x) (slope of tangent) f ( x ) Value of y Shape of the graph