It would be a good idea to try to sketch some of the cubics first before trying to form an equation.
Can you find a cubic curve that…
… has no stationary points?
… has two stationary points: one when \(x=2\) and another when \(x=5\)?
… has a local minimum when \(x=-1\)?
… has a local minimum when \(x=-2\) and a local maximum when \(x=4\)?