(+1)+(-3)+(+5)+(-7).+(+2005)+(-2007)+(+2009)+(-2011)=

问题描述:

(+1)+(-3)+(+5)+(-7).+(+2005)+(-2007)+(+2009)+(-2011)=

原式
= (1 - 3) + (5 - 7) + ...+ (2005 - 2007) + (2009 - 2011)
= (-2) + (-2) + ...+ (-2) + (-2)
= (-2) × 503
= -1006