The functions f and g are defined for all real values of \(x\) by
$$f(x) = 4x^2 - 12x \quad \text{and} \quad g(x) = ax + b,$$
where \(a\) and \(b\) are non-zero constants.
- Find the range of f. [3]
- Explain why the function f has no inverse. [2]
- Given that \(g^{-1}(x) = g(x)\) for all values of \(x\), show that \(a = -1\). [4]
- Given further that gf\((x) < 5\) for all values of \(x\), find the set of possible values of \(b\). [4]