{an}是等差数列,前n项和为Sn,且S2011/2011-S2009/2009=1,则公差d为?
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![{an}是等差数列,前n项和为Sn,且S2011/2011-S2009/2009=1,则公差d为?](/uploads/image/z/13418246-38-6.jpg?t=%7Ban%7D%E6%98%AF%E7%AD%89%E5%B7%AE%E6%95%B0%E5%88%97%2C%E5%89%8Dn%E9%A1%B9%E5%92%8C%E4%B8%BASn%2C%E4%B8%94S2011%2F2011-S2009%2F2009%3D1%2C%E5%88%99%E5%85%AC%E5%B7%AEd%E4%B8%BA%3F)
{an}是等差数列,前n项和为Sn,且S2011/2011-S2009/2009=1,则公差d为?
{an}是等差数列,前n项和为Sn,且S2011/2011-S2009/2009=1,则公差d为?
{an}是等差数列,前n项和为Sn,且S2011/2011-S2009/2009=1,则公差d为?
S2011/2011=(a1+a2011)/2
S2009/2009=(a1+a2009)/2
S2011/2011-S2009/2009
=(a1+a2011)/2-(a1+a2009)/2
=1/2(a2011-a2009)
=1/2 x 2d=d
∴d=1
1