\begin{enumerate} \item (a) Show that \(( x + 2 )\) is a factor of \(\mathrm { f } ( x ) = x ^ { 3 } - 19 x - 30\).
(b) Factorise \(\mathrm { f } ( x )\) completely. \item For the binomial expansion, in descending powers of \(x\), of \(\left( x ^ { 3 } - \frac { 1 } { 2 x } \right) ^ { 12 }\),