令a=2013
原式=[a³-2a²-(a-2)]/[a³+a²-(a+1)]
=[a²(a-2)-(a-2)]/[a²(a+1)-(a+1)]
=(a-2)(a²-1)/(a+1)(a²-1)
=(a-2)/(a+1)
=2011/2014