3 It is given that \(( x + 1 )\) and \(( x - 3 )\) are two factors of \(\mathrm { f } ( x )\), where
$$\mathrm { f } ( x ) = p x ^ { 3 } - 3 x ^ { 2 } - 8 x + q$$
3
- Find the values of \(p\) and \(q\).
[0pt]
[3 marks]
3 - Fully factorise f (x).
\section*{Fully justify your answer.}