4 The polynomial \(\mathrm { f } ( x )\) is defined by
$$f ( x ) = 12 x ^ { 3 } + 25 x ^ { 2 } - 4 x - 12$$
- Show that \(\mathrm { f } ( - 2 ) = 0\) and factorise \(\mathrm { f } ( x )\) completely.
- Given that
$$12 \times 27 ^ { y } + 25 \times 9 ^ { y } - 4 \times 3 ^ { y } - 12 = 0$$
state the value of \(3 ^ { y }\) and hence find \(y\) correct to 3 significant figures.