9 Let \(\mathrm { f } ( x ) = \frac { x ^ { 2 } + 7 x - 6 } { ( x - 1 ) ( x - 2 ) ( x + 1 ) }\).
- Express \(\mathrm { f } ( x )\) in partial fractions.
- Show that, when \(x\) is sufficiently small for \(x ^ { 4 }\) and higher powers to be neglected,
$$f ( x ) = - 3 + 2 x - \frac { 3 } { 2 } x ^ { 2 } + \frac { 11 } { 4 } x ^ { 3 } .$$