设数列[an}的前n项和为Sn,a1=a ,a2=p(p>0),Sn=n(an-a1)/2(1)求a的值(2)求证 数列{an}是等差数列(3) 求证 (an -1)/(an+1)<1

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设数列[an}的前n项和为Sn,a1=a ,a2=p(p>0),Sn=n(an-a1)/2(1)求a的值(2)求证 数列{an}是等差数列(3) 求证 (an -1)/(an+1)<1

设数列[an}的前n项和为Sn,a1=a ,a2=p(p>0),Sn=n(an-a1)/2(1)求a的值(2)求证 数列{an}是等差数列(3) 求证 (an -1)/(an+1)<1
设数列[an}的前n项和为Sn,a1=a ,a2=p(p>0),Sn=n(an-a1)/2
(1)求a的值
(2)求证 数列{an}是等差数列
(3) 求证 (an -1)/(an+1)<1

设数列[an}的前n项和为Sn,a1=a ,a2=p(p>0),Sn=n(an-a1)/2(1)求a的值(2)求证 数列{an}是等差数列(3) 求证 (an -1)/(an+1)<1
(1)S1=1(a1-a1)/2=0=a1=a
所以a=0
(2)因为a1=0,所以Sn=n(an+a1)/2
所以an为等差数列
(3)d=a2-a1=p>0
所以an-1

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