Respuesta :

This is an arithmetic sequence with first term -2007 and common difference of 1. and last term = 2009.  Total number of terms = 2008 + 2009 =  4017

Sn = (n/2)(a + l)

Sum (4017/2) ( -2007 + 2009) = 4017 * 2 / 2  = 4017 Answer