A.4 | B.5 | C.6 | D.7 |
|
A.成等差数列不成等比数列 |
B.成等比数列不成等差数列 |
C.成等差数列又成等比数列 |
D.既不成等差数列又不成等比数列 |
S2009 |
2009 |
S2007 |
2007 |
A.-2008 | B.2008 | C.-2010 | D.2010 |
A.公差为-1的等差数列 | B.公差为5的等差数列 |
C.首项为5的等差数列 | D.公差为n的等差数列 |
A.a1+a101>0 | B.a2+a102<0 | C.a3+a99=0 | D.a51=51 |
A.{an}递增,Sn有最大值 | B.{an}递增,Sn有最小值 |
C.{an}递减,Sn有最大值 | D.{an}递减,Sn有最小值 |
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