专题九等差数列
命题趋势:
典型例题:
例1:(1)等差数列
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<Object: word/embeddings/oleObject2.bin>
A.<Object: word/embeddings/oleObject3.bin>
B.<Object: word/embeddings/oleObject4.bin>
C.<Object: word/embeddings/oleObject5.bin>
D.<Object: word/embeddings/oleObject6.bin>
(2)已知数列
{an}为等差数列,且
a4+a8+a10=50,则a2+2a10=_________
练习1:等差数列
{an}的第3项是5,第8项是20,则通项公式为
___________
(2)在数列{an}中,若a1=1,an+1=an+2(n∈N*),则该数列的通项公式为
_________
例2:已知等差数列
{an}满足a1=10,an=50,Sn=420,则n=________,
d=__________
练 ...


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