等差数列 a1=-2008,S2008/2008-S2006/2006=2,求S2010
问题描述:
等差数列 a1=-2008,S2008/2008-S2006/2006=2,求S2010
答
s2008=2008[-2008+(-2008+2007d)]/2s2006=2006[-2008+(-2008+2005d)]/2(s2008)/2008-(s2006)/2006=2007d/2-2005d/2=d=2∴s2010=2010[-2008+(-2008+2009d)]/2=2010(-2008+2009)=2010