数列{an}中,a1=2,a(n+1)=an+cn,(c是常数,n=1,2,3,…),且a1,a2,a3成公比不为1的等比数列.(1)求c的值 ...数列{an}中,a1=2,a(n+1)=an+cn,(c是常数,n=1,2,3,…),且a1,a2,a3成公比不为1的等比数列.(1)求c的值(2)求{an}的通项
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![数列{an}中,a1=2,a(n+1)=an+cn,(c是常数,n=1,2,3,…),且a1,a2,a3成公比不为1的等比数列.(1)求c的值 ...数列{an}中,a1=2,a(n+1)=an+cn,(c是常数,n=1,2,3,…),且a1,a2,a3成公比不为1的等比数列.(1)求c的值(2)求{an}的通项](/uploads/image/z/8836609-49-9.jpg?t=%E6%95%B0%E5%88%97%7Ban%7D%E4%B8%AD%2Ca1%3D2%2Ca%28n%2B1%29%3Dan%2Bcn%2C%28c%E6%98%AF%E5%B8%B8%E6%95%B0%2Cn%3D1%2C2%2C3%2C%E2%80%A6%29%2C%E4%B8%94a1%2Ca2%2Ca3%E6%88%90%E5%85%AC%E6%AF%94%E4%B8%8D%E4%B8%BA1%E7%9A%84%E7%AD%89%E6%AF%94%E6%95%B0%E5%88%97.%281%29%E6%B1%82c%E7%9A%84%E5%80%BC+...%E6%95%B0%E5%88%97%7Ban%7D%E4%B8%AD%2Ca1%3D2%2Ca%28n%2B1%29%3Dan%2Bcn%2C%28c%E6%98%AF%E5%B8%B8%E6%95%B0%2Cn%3D1%2C2%2C3%2C%E2%80%A6%29%2C%E4%B8%94a1%2Ca2%2Ca3%E6%88%90%E5%85%AC%E6%AF%94%E4%B8%8D%E4%B8%BA1%E7%9A%84%E7%AD%89%E6%AF%94%E6%95%B0%E5%88%97.%281%29%E6%B1%82c%E7%9A%84%E5%80%BC%282%29%E6%B1%82%7Ban%7D%E7%9A%84%E9%80%9A%E9%A1%B9)
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数列{an}中,a1=2,a(n+1)=an+cn,(c是常数,n=1,2,3,…),且a1,a2,a3成公比不为1的等比数列.(1)求c的值 ...数列{an}中,a1=2,a(n+1)=an+cn,(c是常数,n=1,2,3,…),且a1,a2,a3成公比不为1的等比数列.(1)求c的值(2)求{an}的通项
数列{an}中,a1=2,a(n+1)=an+cn,(c是常数,n=1,2,3,…),且a1,a2,a3成公比不为1的等比数列.(1)求c的值 ...
数列{an}中,a1=2,a(n+1)=an+cn,(c是常数,n=1,2,3,…),且a1,a2,a3成公比不为1的等比数列.
(1)求c的值
(2)求{an}的通项公式.
数列{an}中,a1=2,a(n+1)=an+cn,(c是常数,n=1,2,3,…),且a1,a2,a3成公比不为1的等比数列.(1)求c的值 ...数列{an}中,a1=2,a(n+1)=an+cn,(c是常数,n=1,2,3,…),且a1,a2,a3成公比不为1的等比数列.(1)求c的值(2)求{an}的通项
a1=2,a2=2+c,a3=2+3c,
a1*a3=a2^2,
2*(2+3c)=(2+c)^2,
c=2
a2-a1=2*1
a3-a2=2*2
a4-a3=2*3
...
a(n)-a(n-1)=2*(n-1)
累加有
a(n)-a1=2*(n(n-1)/2)=n^2-n
a(n)=n^2-n+2