已知两个等差数列{an}{bn},其前n项的和分别为Sn和Tn,并且Sn/Tn=7n+2/n+3,则a7/b8=
来源:学生作业帮 编辑:搜搜考试网作业帮 分类:数学作业 时间:2024/07/26 13:56:48
已知两个等差数列{an}{bn},其前n项的和分别为Sn和Tn,并且Sn/Tn=7n+2/n+3,则a7/b8=
![已知两个等差数列{an}{bn},其前n项的和分别为Sn和Tn,并且Sn/Tn=7n+2/n+3,则a7/b8=](/uploads/image/z/17714382-6-2.jpg?t=%E5%B7%B2%E7%9F%A5%E4%B8%A4%E4%B8%AA%E7%AD%89%E5%B7%AE%E6%95%B0%E5%88%97%EF%BD%9Ban%EF%BD%9D%EF%BD%9Bbn%EF%BD%9D%2C%E5%85%B6%E5%89%8Dn%E9%A1%B9%E7%9A%84%E5%92%8C%E5%88%86%E5%88%AB%E4%B8%BASn%E5%92%8CTn%2C%E5%B9%B6%E4%B8%94Sn%2FTn%3D7n%2B2%2Fn%2B3%2C%E5%88%99a7%2Fb8%3D)
sn=(n/2)(a1+an),Tn=(n/2)(b1+bn),设an公差为d1,bn公差为d2
Sn/Tn=(a1+an)/(b1+bn)=(nd1+a1-d1)/(nd2+b1-d2)=(7n+2)/(n+3)
令d2=m,m≠0,则d1=7m,a1-d1=2m,b1-d2=3m
得a1=9m,b1=4m
a7=a1+6d1=9m+42m=51m
b8=b1+7d2=4m+7m=11m
a7/b8=51m/11m=51/11 答案是31/6
Sn/Tn=(a1+an)/(b1+bn)=(nd1+a1-d1)/(nd2+b1-d2)=(7n+2)/(n+3)
令d2=m,m≠0,则d1=7m,a1-d1=2m,b1-d2=3m
得a1=9m,b1=4m
a7=a1+6d1=9m+42m=51m
b8=b1+7d2=4m+7m=11m
a7/b8=51m/11m=51/11 答案是31/6
1.已知两个等差数列{An},{Bn},其前n项和分别为Sn,Tn,并且Sn/Tn=(7n+2)/(n+3).求a7/b
{an},{bn}是两个等差数列,其前n项和分别为Sn和Tn,且Sn/Tn=(7n+2)/(n+3),则a8/b8=
设两个等差数列{an},{bn}的前n项和分别为Sn,Tn.若Sn/Tn=7n+1/4n+27,则a7/b7=
...求正解等差数列{an}、{bn}的前n项和分别为Sn、Tn,若Sn/Tn=2n+2/n+3,则 a7/b7=?(_
已知两个等差数列{an},{bn}的前n项和分别是Sn,Tn,若 Sn/Tn =(2n)/(3n+1),则 an/bn=
等差数列{an}{bn}的前n项和分别为Sn,Tn 若Sn/Tn=2n/3n+1 求a7/b3
1.已知两个等差数列An,Bn,前n项和分别为Sn,Tn,且Sn/Tn=(2n+2)/(n+2),则An/Bn=
若两个等差数列{An}和{Bn}的前n项和分别是Sn、Tn,已知Sn/Tn=7n/(n+3),则a5/b4=
若两个等差数列{An}和{Bn}的前n项和分别是Sn、Tn,已知Sn/Tn=7n/(n+3),则a5/a6=
两个等差数列{an}和{bn}的前n项和分别是Sn,Tn,已知Sn/Tn=7n/(n+3),则a5/b5等于?
两个等差数列{an},{bn}的前n项和分别为Sn,Tn,若Sn/Tn=2n/3n+1,求an/bn.
已知等差数列{an}、{bn}的前n项和分别为Sn、Tn,若Sn/Tn=【7n+1】/【4n+27】,则an/bn=