数列【An】的前n项和Sn=n^2-9n,第K项满足Ak大于5小于8,则K=?
已知数列{an}的前n项和Sn=n^2-9n,第k项满足5<ak<8,则k等于
已知数列{An}的前n项和Sn=n平方-9n,第k项满足5<Ak<8,则k等于
已知数列an前n项和Sn=n^2-9n,第k项满足5<ak<8,则k等于多少
已知数列{an}满足ak+a(n-k)=2,(k,n-k∈N*),则数列{an}的前n项和Sn=
已知数列{an}的前n项和Sn=n^2-9n,则其通项an=多少;若它的第k项满足5<ak<8,则k=多少
已知数列{an}的前n项和Sn=n^2-9n 第K项满足5
已知数列{An}的前n项和Sn等于n平方减9n,第k项满足5<Ak
已知数列an的前n项和Sn=n^2-9n,第k项满足5
已知数列{An }的前 n项和Sn=nxn-9n ,第 k项满足5
已知各项大于零的数列{ak}的前k项和为Sk,且∑(上面是n,下面是k=1)ak^3(k为下标)=Sn^2,求数列通项
已知数列an中 前n项和sn=2n^2+k 求通项an
数列an的前n项和Sn满足:Sn=2an-3n