1)A1=1,An+1=3An—5*3^n ,则An=?2)已知数列An,A1=1,An=2Sn^2/2Sn – 1,求Sn与An.希望有过程及思路,
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1)A1=1,An+1=3An—5*3^n ,则An=?2)已知数列An,A1=1,An=2Sn^2/2Sn – 1,求Sn与An.希望有过程及思路,
1)A1=1,An+1=3An—5*3^n ,则An=?
2)已知数列An,A1=1,An=2Sn^2/2Sn – 1,求Sn与An.
希望有过程及思路,
1)A1=1,An+1=3An—5*3^n ,则An=?2)已知数列An,A1=1,An=2Sn^2/2Sn – 1,求Sn与An.希望有过程及思路,
A1=1,An+1=3An—5*3^n ,则An=10
已知数列An,A1=1,An=2Sn^2/2Sn – 1,求Sn与An=15,20
1,An+1+m=3(An+m)=3An+3m
An+1=3An+2m
2m=-5*3^n
m=-5*3^n/2
An+1-5*3^n/2=3(An-5*3^n/2)
Bn+1=3Bn
B1=A1-5*3/2=-6.5
现在会做吗?
2,用公式An=Sn-Sn-1
An=2Sn^2/2Sn – 1
2Sn^2-Sn-2...
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1,An+1+m=3(An+m)=3An+3m
An+1=3An+2m
2m=-5*3^n
m=-5*3^n/2
An+1-5*3^n/2=3(An-5*3^n/2)
Bn+1=3Bn
B1=A1-5*3/2=-6.5
现在会做吗?
2,用公式An=Sn-Sn-1
An=2Sn^2/2Sn – 1
2Sn^2-Sn-2SnSn-1+Sn-1=2Sn^2
Sn-Sn-1=-2SnSn-1
除以SnSn-1
1/Sn-1-1/Sn=-2
Bn-1-Bn=-2
等差数列
现在会做吗?
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