(2014•齐齐哈尔三模)等差数列{an}的前n项和为Sn,且S3=6,a1=4,则公差d等于(  ) A.1 B.53 C.-2 D.3

问题描述:

(2014•齐齐哈尔三模)等差数列{an}的前n项和为Sn,且S3=6,a1=4,则公差d等于(  )
A. 1
B.

5
3

C. -2
D. 3

∵S3=6=

3
2
(a1+a3),且 a3=a1+2d,a1=4,∴d=-2,
故选C.