First term = a = 2006
2nd term = a + d = 1998, so d = -8.
Let n be the term = 0, so
0 = 2006 + (n-1)(-8) = 2006 - 8n + 8
8n = 2014
n = 251.75
that means the first term is negative when n = 252.
= 2006 + (252 -1)(-8)
= 2006 - (251)(8)
= 2006 - 2008
= -2.