Answer
$n^3-3n^2+2n$
Work Step by Step
Since,we have $\dfrac{n!}{(n-3)!}$
Thus,
$\dfrac{n!}{(n-3)!}=\dfrac{n \cdot (n-1) \cdot (n-2) \cdot (n-3) !}{(n-3)!}$
or, $=n(n-1)(n-2)$
or, $=n(n^2-3n+2)$
or, $=n^3-3n^2+2n$
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