The diagram shows the graph of `y = f(x)` over the domain `-2 leq x leq 4`.

The function can be expressed as `f(x) = ax<sup>3</sup> + bx<sup>2</sup>`, where `a` and `b` are integers.

Find the value of `a` and `b`.

Using the graph, or otherwise, solve the equation `f(x) = 6`, giving your answer(s) to `1` decimal place.