geeft .
Use the graph or a sign scheme of to find that there are two extrema, namely min. and max. .
gives .
Use the graph or a sign scheme of to conclude that there is one inflection point, namely .
geeft .
gives . This equation has two solutions, so there is one more point on the graph in which the slope of the tangent to the graph equals .
geeft .
The graph of shows that the maximum volume occurs when cm.
gives .
And gives: .
For the derivative does not have a sign change, both to the left and to the right of the graph of is increasing.