(1+2+3+4+5+······)/(1-1/1004)(1-1/1005)(1-1/1006)(1-1/1007)·
(1+1/2)(1-1/3)(1+1/4)(1-1/5)··········(1-1/2005)(1+1/2006)=_
计算(+1)+(-2)+(+3)+(-4)+······+(-100)+(+101)+(-102)
计算 1-2+3-4+5-6+····+(-1)^n+1*n
求(2+5+8······+2000)-(1+4+7······+1999)的值.【简算】
(1)用像······似的······造个句子 (2)用像······一样······造一个句子
1、(1+3+5+···+2009+2011)-(2+4+6+···+2010+2012)
1+3+5+···+(2n+3)
1+(-2)+3+(-4)···········+99-100等于多少
计算:-1+2+(-3)+4+(-5)+······+(-99)+100等于多少?
根据1+2+3+4+······+n=n(n+1)/2 计算2+4+6+····+200
求证;1+1/2+1/3+······+1/k≧(2k)/(k+1)
(1+3+5+···+997+999)—(2+4+6+···+998+1000)