Go to https://www.geogebra.org/graphing?lang=es
Type your function and press enter, the graph will be shown, just as it is in the picture, I will show you what you have to type
[tex]f(x)=-4x^3-13.92x^2+102.9228x-0.15;\text{ -15}\leq x\leq15[/tex]
Here is where you have to do it, press enter after that
Now, on the next line, type Extremum(f) and press enter
On the next line type Root(f), press enter
On the next line type f(0), press enter
Now, let's interpret the information
q(c) intercept will be f(0), it has a value of -0.15
c intercepts are the abscissas of C, D and E, these are -7.103, 0.001 and 3.621 respectively
the local minimum is A, so q has a local minimum of -382.075 that occurs at c=-4.31
the local maximum is B, so q has a local maximum of 118.019 that occurs at c=1.99
q is increasing on the interval (-4.31, 1.99)
q is decreasing on the intervals [-15, -4.31) and (1.99, 15]
