因为这样求得的d只能保证2a2=a1+a3,也就是前3项成等差数列,并不能保证3项之后.
可以以较为普遍的情况来分析.
记数列{an}的前n项和为Sn,若{Sn/an}是公差为d的等差数列,则{an}为等差数列的充要条件是d=?
2个回答
相关问题
-
记数列{an}的前n项和为Sn,若{Sn/an}是公差为d的等差数列,则{an}为等差数列时d=
-
记数列{an}的前n项和为Sn，若{Snan}是公差为d的等差数列，则{an}为等差数列的充要条件是d=______．
-
等差数列的性质：若{an}是公差为d的等差数列,则数列{sn/n}也是等差数列,且公差为____?
-
设等差数列{an}公差d是2,前n项和为Sn,则lim(an^2-n^2)/Sn
-
证明：数列{an}为等差数列的充要条件是{an}前n项和Sn=An^2+Bn
-
已知等差数列｛an｝的前n项和为Sn,公差为d.
-
记等差数列{an}前n项和为Sn,若|a3|=|a11|,且公差d
-
设数列｛an｝的前n项和为sn,证明：｛an｝为等差数列的充要条件是对任意的n∈N﹢,Sn=[n(a₁+an
-
设数列{an}的前n项和为sn,求证:sn=An^2+Bn(A,B为常数）是{an}为等差数列的充要条件.
-
记等差数列{an}前n项和为Sn,求证{Sn/n}为等差数列?