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等差数列{an}中,若口a1=2,a3=6,则a2= ()A.3 B.4C.8 D.12
等差数列{an}中,若口a1=2,a3=6,则a2= ()
A.3
B.4
C.8
D.12
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等差数列{an}中,若口a1=2,a3=6,则a2= ()
A.3
B.4
C.8
D.12
已知等差数列的公差d≠0,a1=1/2,且a1,a2,a5成等比数列.
(I)求{an}的通项公式;
(Ⅱ)若{an}的前n项和Sn=50,求n
请帮忙给出每个问题的正确答案和分析,谢谢!