Question

How would you do this: Graphs A and B are approximate graphs of f and fI for F(x)=x^2(x-12). Graph A: https://kiva.math.nau.edu/webwork2_course_files/CLouchart_136/tmp/gif/kmd329-3182-setHomework_10prob6image1.png Graph B:https://kiva.math.nau.edu/webwork2_course_files/CLouchart_136/tmp/gif/kmd329-3182-setHomework_10prob6image2.png
So f is decreasing (and fI is negative) on the interval (0,a) for a=