题目内容：

1+2-3-4+5+6-7-8+9+10-11-12+.+1997+1998-1999-2000+2001=?

优质解答

1+2-3-4+5+6-7-8+9+10-11-12+.+1997+1998-1999-2000+2001 = (1 +2 - 3 - 4) +( 5 +6 - 7- 8) + (9 +10 - 11-12) + ...+ (1997 + 1998 - 1999 - 2000) +2001 = (-4) + (-4) + (-4) + .+ (-4) + 2001 = (-4) * 500 + 2001 = - 2000 + 2001 = 1