設(shè)是等差數(shù)列的前項(xiàng)和.又.則= 查看更多

 

題目列表(包括答案和解析)

設(shè)數(shù)列{an}的前n項(xiàng)和為Sn(n∈N),關(guān)于數(shù)列{an}有下列三個(gè)命題:

(1)若{an}既是等差數(shù)列又是等比數(shù)列,則an=an+1(n∈N+);

(2)若Sn=an2+bn(a、b∈R),則{an}是等差數(shù)列;

(3)若Sn=1-(-1)n,則{an}是等比數(shù)列.

這些命題中,真命題的序號(hào)是________.

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設(shè)數(shù)列{an}的前n項(xiàng)和為Sn(n∈N+).關(guān)于數(shù)列{an}有下列三個(gè)命題:

①若{an}既是等差數(shù)列又是等比數(shù)列,則an=an+1(n∈N+);

②若Sn=an2+bn(a、b∈R),則{an}是等差數(shù)列;

③若Sn=1-(-1)n,則{an}是等比數(shù)列.

這些命題中,真命題的序號(hào)是________.

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設(shè)數(shù)列{an}的前n項(xiàng)和為Sn(n∈N*).關(guān)于數(shù)列{an}有下列三個(gè)命題:

①若{an}既是等差數(shù)列又是等比數(shù)列,則an=an+1(n∈N*);

②若Sn=an2+bn(a、b∈R),則{an}是等差數(shù)列;

③若Sn=1-(-1)n,則{an}是等比數(shù)列.

這些命題中,真命題的序號(hào)是________.

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設(shè)數(shù)列{an}的前n項(xiàng)和為Sn(n∈N*),關(guān)于數(shù)列{an}有下列三個(gè)命題:

①若{an}既是等差數(shù)列又是等比數(shù)列,則an=an+1(n∈N*);

②若Sn=an2+bn(a、b∈R),則{an}是等差數(shù)列;

③若Sn=1-(-1)n,則{an}是等比數(shù)列.

這些命題中,真命題的序號(hào)是________.

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設(shè)數(shù)列{}的前n項(xiàng)和為Sn(n∈N?),關(guān)于數(shù)列{}有下列四個(gè)命題:

(1)若{}既是等差數(shù)列又是等比數(shù)列,則an=an+1(n∈N*);

(2)若Sn=An2+Bn(A,B∈R,A、B為常數(shù)),則{}是等差數(shù)列;

(3)若Sn=1-(-1)n,則{}是等比數(shù)列;

(4)若{}是等比數(shù)列,則Sm,S2m-Sm,S3m-S2m(m∈N*)也成等比數(shù)列;其中正確的命題的個(gè)數(shù)是

    A.4              B.3              C.2              D.1

 

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