m-2m-3m+4m-5m-6m+7m-8m-9m+.+2002m-2003m-2004m

问题描述:

m-2m-3m+4m-5m-6m+7m-8m-9m+.+2002m-2003m-2004m

等差数列求和,每三项合并,有668项,就可以用一加二一直加到一百的方法算了