摘要:1) 若成等比数列.则也成等比数列,
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设数列{
}的前n项和为Sn(n∈N?),关于数列{
}有下列四个命题:
(1)若{
}既是等差数列又是等比数列,则an=an+1(n∈N*);
(2)若Sn=An2+Bn(A,B∈R,A、B为常数),则{
}是等差数列;
(3)若Sn=1-(-1)n,则{
}是等比数列;
(4)若{
}是等比数列,则Sm,S2m-Sm,S3m-S2m(m∈N*)也成等比数列;其中正确的命题的个数是
A.4 B.3 C.2 D.1
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设数列{
}的前n项和为Sn(n∈N?),关于数列{
}有下列四个命题:
(1)若{
}既是等差数列又是等比数列,则an=an+1(n∈N*);
(2)若Sn=An2+Bn(A,B∈R,A、B为常数),则{
}是等差数列;
(3)若Sn=1-(-1)n,则{
}是等比数列;
(4)若{
}是等比数列,则Sm,S2m-Sm,S3m-S2m(m∈N*)也成等比数列;其中正确的命题的个数是
A.4 B.3 C.2 D.1
(1)若{
(2)若Sn=An2+Bn(A,B∈R,A、B为常数),则{
(3)若Sn=1-(-1)n,则{
(4)若{
A.4 B.3 C.2 D.1