Question 751451
{{{(n + 1)!/(n - 2)! }}} = {{{(n + 1)(n)(n - 1)(n - 2)!/(n - 2)!}}}
= {{{(n + 1)(n)(n - 1)cross((n - 2)!)/(cross((n - 2)!))}}} 
= {{{(n + 1)(n)(n - 1)}}} 
= {{{n^3 - n}}}, the right hand side ■