等差数列an中 a1003+a1004+a1005+a1006=2 则该数列的前2008项和为?
问题描述:
等差数列an中 a1003+a1004+a1005+a1006=2 则该数列的前2008项和为?
答
等差数列a1+a2008=(a1003+a1004+a1005+a1006)/2=1
等差数列和=(a1+a2008)*2008/2=1004