3 The polynomial \(x ^ { 4 } - 6 x ^ { 2 } + x + a\) is denoted by \(\mathrm { f } ( x )\).
- It is given that \(( x + 1 )\) is a factor of \(\mathrm { f } ( x )\). Find the value of \(a\).
- When \(a\) has this value, verify that ( \(x - 2\) ) is also a factor of \(\mathrm { f } ( x )\) and hence factorise \(\mathrm { f } ( x )\) completely.